Random access process in carrier aggregation

ABSTRACT

A MAC layer instructs a physical layer to transmit a preamble as a part of a random access (RA) procedure on a licensed assisted access (LAA) cell. The wireless device performs an LBT for transmission of the preamble. The wireless device considers the RA procedure unsuccessfully completed if a first condition based on a first counter is met. The wireless device considers the RA procedure unsuccessfully completed if a condition based on a second counter is met.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/188,694, filed Jul. 5, 2015, which is hereby incorporated byreference in its entirety.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Examples of several of the various embodiments of the present inventionare described herein with reference to the drawings.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers in a carrier group as per an aspect of anembodiment of the present invention.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention.

FIG. 4 is a block diagram of a base station and a wireless device as peran aspect of an embodiment of the present invention.

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present invention.

FIG. 6 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present invention.

FIG. 7 is an example diagram for a protocol structure with CA and DC asper an aspect of an embodiment of the present invention.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present invention.

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentinvention.

FIG. 10 is an example grouping of cells into PUCCH groups as per anaspect of an embodiment of the present invention.

FIG. 11 illustrates example groupings of cells into one or more PUCCHgroups and one or more TAGs as per an aspect of an embodiment of thepresent invention.

FIG. 12 illustrates example groupings of cells into one or more PUCCHgroups and one or more TAGs as per an aspect of an embodiment of thepresent invention.

FIG. 13 is an example MAC PDU as per an aspect of an embodiment of thepresent invention.

FIG. 14 is an example signal flow of a random access process on alicensed cell as per an aspect of an embodiment of the presentinvention.

FIG. 15 is an example signal flow of a random access process as per anaspect of an embodiment of the present invention.

FIG. 16 is an example signal flow of a random access process as per anaspect of an embodiment of the present invention.

FIG. 17 is an example signal flow of a random access process as per anaspect of an embodiment of the present invention.

FIG. 18 is an example signal flow of a random access process as per anaspect of an embodiment of the present invention.

FIG. 19 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 20 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 21 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 22 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 23 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 24 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 25 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

FIG. 26 is an example flow diagram of a random access process as per anaspect of an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Example embodiments of the present invention enable operation of carrieraggregation. Embodiments of the technology disclosed herein may beemployed in the technical field of multicarrier communication systems.More particularly, the embodiments of the technology disclosed hereinmay relate to operation of uplink transmissions and/or random accessprocesses in a carrier aggregation.

The following Acronyms are used throughout the present disclosure:

ASIC application-specific integrated circuit

BPSK binary phase shift keying

CA carrier aggregation

CSI channel state information

CDMA code division multiple access

CSS common search space

CPLD complex programmable logic devices

CC component carrier

DL downlink

DCI downlink control information

DC dual connectivity

EPC evolved packet core

E-UTRAN evolved-universal terrestrial radio access network

FPGA field programmable gate arrays

FDD frequency division multiplexing

HDL hardware description languages

HARQ hybrid automatic repeat request

IE information element

LAA licensed assisted access

LTE long term evolution

MCG master cell group

MeNB master evolved node B

MIB master information block

MAC media access control

MAC media access control

MME mobility management entity

NAS non-access stratum

OFDM orthogonal frequency division multiplexing

PDCP packet data convergence protocol

PDU packet data unit

PHY physical

PDCCH physical downlink control channel

PHICH physical HARQ indicator channel

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

PCell primary cell

PCell primary cell

PCC primary component carrier

PSCell primary secondary cell

pTAG primary timing advance group

QAM quadrature amplitude modulation

QPSK quadrature phase shift keying

RBG Resource Block Groups

RLC radio link control

RRC radio resource control

RA random access

RB resource blocks

SCC secondary component carrier

SCell secondary cell

Scell secondary cells

SCG secondary cell group

SeNB secondary evolved node B

sTAGs secondary timing advance group

SDU service data unit

S-GW serving gateway

SRB signaling radio bearer

SC-OFDM single carrier-OFDM

SFN system frame number

SIB system information block

TAI tracking area identifier

TAT time alignment timer

TDD time division duplexing

TDMA time division multiple access

TA timing advance

TAG timing advance group

TB transport block

UL uplink

UE user equipment

VHDL VHSIC hardware description language

Example embodiments of the invention may be implemented using variousphysical layer modulation and transmission mechanisms. Exampletransmission mechanisms may include, but are not limited to: CDMA, OFDM,TDMA, Wavelet technologies, and/or the like. Hybrid transmissionmechanisms such as TDMA/CDMA, and OFDM/CDMA may also be employed.Various modulation schemes may be applied for signal transmission in thephysical layer. Examples of modulation schemes include, but are notlimited to: phase, amplitude, code, a combination of these, and/or thelike. An example radio transmission method may implement QAM using BPSK,QPSK, 16-QAM, 64-QAM, 256-QAM, and/or the like. Physical radiotransmission may be enhanced by dynamically or semi-dynamically changingthe modulation and coding scheme depending on transmission requirementsand radio conditions.

FIG. 1 is a diagram depicting example sets of OFDM subcarriers as per anaspect of an embodiment of the present invention. As illustrated in thisexample, arrow(s) in the diagram may depict a subcarrier in amulticarrier OFDM system. The OFDM system may use technology such asOFDM technology, SC-OFDM technology, or the like. For example, arrow 101shows a subcarrier transmitting information symbols. FIG. 1 is forillustration purposes, and a typical multicarrier OFDM system mayinclude more subcarriers in a carrier. For example, the number ofsubcarriers in a carrier may be in the range of 10 to 10,000subcarriers. FIG. 1 shows two guard bands 106 and 107 in a transmissionband. As illustrated in FIG. 1, guard band 106 is between subcarriers103 and subcarriers 104. The example set of subcarriers A 102 includessubcarriers 103 and subcarriers 104. FIG. 1 also illustrates an exampleset of subcarriers B 105. As illustrated, there is no guard band betweenany two subcarriers in the example set of subcarriers B 105. Carriers ina multicarrier OFDM communication system may be contiguous carriers,non-contiguous carriers, or a combination of both contiguous andnon-contiguous carriers.

FIG. 2 is a diagram depicting an example transmission time and receptiontime for two carriers as per an aspect of an embodiment of the presentinvention. A multicarrier OFDM communication system may include one ormore carriers, for example, ranging from 1 to 10 carriers. Carrier A 204and carrier B 205 may have the same or different timing structures.Although FIG. 2 shows two synchronized carriers, carrier A 204 andcarrier B 205 may or may not be synchronized with each other. Differentradio frame structures may be supported for FDD and TDD duplexmechanisms. FIG. 2 shows an example FDD frame timing. Downlink anduplink transmissions may be organized into radio frames 201. In thisexample, radio frame duration is 10 msec. Other frame durations, forexample, in the range of 1 to 100 msec may also be supported. In thisexample, each 10 ms radio frame 201 may be divided into ten equallysized subframes 202. Other subframe durations such as including 0.5msec, 1 msec, 2 msec, and 5 msec may also be supported. Subframe(s) mayconsist of two or more slots (e.g. slots 206 and 207). For the exampleof FDD, 10 subframes may be available for downlink transmission and 10subframes may be available for uplink transmissions in each 10 msinterval. Uplink and downlink transmissions may be separated in thefrequency domain. Slot(s) may include a plurality of OFDM symbols 203.The number of OFDM symbols 203 in a slot 206 may depend on the cyclicprefix length and subcarrier spacing.

FIG. 3 is a diagram depicting OFDM radio resources as per an aspect ofan embodiment of the present invention. The resource grid structure intime 304 and frequency 305 is illustrated in FIG. 3. The quantity ofdownlink subcarriers or RBs (in this example 6 to 100 RBs) may depend,at least in part, on the downlink transmission bandwidth 306 configuredin the cell. The smallest radio resource unit may be called a resourceelement (e.g. 301). Resource elements may be grouped into resourceblocks (e.g. 302). Resource blocks may be grouped into larger radioresources called Resource Block Groups (RBG) (e.g. 303). The transmittedsignal in slot 206 may be described by one or several resource grids ofa plurality of subcarriers and a plurality of OFDM symbols. Resourceblocks may be used to describe the mapping of certain physical channelsto resource elements. Other pre-defined groupings of physical resourceelements may be implemented in the system depending on the radiotechnology. For example, 24 subcarriers may be grouped as a radio blockfor a duration of 5 msec. In an illustrative example, a resource blockmay correspond to one slot in the time domain and 180 kHz in thefrequency domain (for 15 KHz subcarrier bandwidth and 12 subcarriers).

FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are example diagrams for uplinkand downlink signal transmission as per an aspect of an embodiment ofthe present invention. FIG. 5A shows an example uplink physical channel.The baseband signal representing the physical uplink shared channel mayperform the following processes. These functions are illustrated asexamples and it is anticipated that other mechanisms may be implementedin various embodiments. The functions may comprise scrambling,modulation of scrambled bits to generate complex-valued symbols, mappingof the complex-valued modulation symbols onto one or severaltransmission layers, transform precoding to generate complex-valuedsymbols, precoding of the complex-valued symbols, mapping of precodedcomplex-valued symbols to resource elements, generation ofcomplex-valued time-domain SC-FDMA signal for each antenna port, and/orthe like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued SC-FDMA baseband signal for each antenna port and/or thecomplex-valued PRACH baseband signal is shown in FIG. 5B. Filtering maybe employed prior to transmission.

An example structure for Downlink Transmissions is shown in FIG. 5C. Thebaseband signal representing a downlink physical channel may perform thefollowing processes. These functions are illustrated as examples and itis anticipated that other mechanisms may be implemented in variousembodiments. The functions include scrambling of coded bits in each ofthe codewords to be transmitted on a physical channel; modulation ofscrambled bits to generate complex-valued modulation symbols; mapping ofthe complex-valued modulation symbols onto one or several transmissionlayers; precoding of the complex-valued modulation symbols on each layerfor transmission on the antenna ports; mapping of complex-valuedmodulation symbols for each antenna port to resource elements;generation of complex-valued time-domain OFDM signal for each antennaport, and/or the like.

Example modulation and up-conversion to the carrier frequency of thecomplex-valued OFDM baseband signal for each antenna port is shown inFIG. 5D. Filtering may be employed prior to transmission.

FIG. 4 is an example block diagram of a base station 401 and a wirelessdevice 406, as per an aspect of an embodiment of the present invention.A communication network 400 may include at least one base station 401and at least one wireless device 406. The base station 401 may includeat least one communication interface 402, at least one processor 403,and at least one set of program code instructions 405 stored innon-transitory memory 404 and executable by the at least one processor403. The wireless device 406 may include at least one communicationinterface 407, at least one processor 408, and at least one set ofprogram code instructions 410 stored in non-transitory memory 409 andexecutable by the at least one processor 408. Communication interface402 in base station 401 may be configured to engage in communicationwith communication interface 407 in wireless device 406 via acommunication path that includes at least one wireless link 411.Wireless link 411 may be a bi-directional link. Communication interface407 in wireless device 406 may also be configured to engage in acommunication with communication interface 402 in base station 401. Basestation 401 and wireless device 406 may be configured to send andreceive data over wireless link 411 using multiple frequency carriers.According to some of the various aspects of embodiments, transceiver(s)may be employed. A transceiver is a device that includes both atransmitter and receiver. Transceivers may be employed in devices suchas wireless devices, base stations, relay nodes, and/or the like.Example embodiments for radio technology implemented in communicationinterface 402, 407 and wireless link 411 are illustrated are FIG. 1,FIG. 2, FIG. 3, FIG. 5, and associated text.

An interface may be a hardware interface, a firmware interface, asoftware interface, and/or a combination thereof. The hardware interfacemay include connectors, wires, electronic devices such as drivers,amplifiers, and/or the like. A software interface may include codestored in a memory device to implement protocol(s), protocol layers,communication drivers, device drivers, combinations thereof, and/or thelike. A firmware interface may include a combination of embeddedhardware and code stored in and/or in communication with a memory deviceto implement connections, electronic device operations, protocol(s),protocol layers, communication drivers, device drivers, hardwareoperations, combinations thereof, and/or the like.

The term configured may relate to the capacity of a device whether thedevice is in an operational or non-operational state. Configured mayalso refer to specific settings in a device that effect the operationalcharacteristics of the device whether the device is in an operational ornon-operational state. In other words, the hardware, software, firmware,registers, memory values, and/or the like may be “configured” within adevice, whether the device is in an operational or nonoperational state,to provide the device with specific characteristics. Terms such as “acontrol message to cause in a device” may mean that a control messagehas parameters that may be used to configure specific characteristics inthe device, whether the device is in an operational or non-operationalstate.

According to some of the various aspects of embodiments, an LTE networkmay include a multitude of base stations, providing a user planePDCP/RLC/MAC/PHY and control plane (RRC) protocol terminations towardsthe wireless device. The base station(s) may be interconnected withother base station(s) (e.g. employing an X2 interface). The basestations may also be connected employing, for example, an S1 interfaceto an EPC. For example, the base stations may be interconnected to theMME employing the S1-MME interface and to the S-G) employing the S1-Uinterface. The S1 interface may support a many-to-many relation betweenMMEs/Serving Gateways and base stations. A base station may include manysectors for example: 1, 2, 3, 4, or 6 sectors. A base station mayinclude many cells, for example, ranging from 1 to 50 cells or more. Acell may be categorized, for example, as a primary cell or secondarycell. At RRC connection establishment/re-establishment/handover, oneserving cell may provide the NAS (non-access stratum) mobilityinformation (e.g. TAI), and at RRC connection re-establishment/handover,one serving cell may provide the security input. This cell may bereferred to as the Primary Cell (PCell). In the downlink, the carriercorresponding to the PCell may be the Downlink Primary Component Carrier(DL PCC), while in the uplink, it may be the Uplink Primary ComponentCarrier (UL PCC). Depending on wireless device capabilities, SecondaryCells (SCells) may be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellmay be a Downlink Secondary Component Carrier (DL SCC), while in theuplink, it may be an Uplink Secondary Component Carrier (UL SCC). AnSCell may or may not have an uplink carrier.

A cell, comprising a downlink carrier and optionally an uplink carrier,may be assigned a physical cell ID and a cell index. A carrier (downlinkor uplink) may belong to only one cell. The cell ID or Cell index mayalso identify the downlink carrier or uplink carrier of the cell(depending on the context it is used). In the specification, cell ID maybe equally referred to a carrier ID, and cell index may be referred tocarrier index. In implementation, the physical cell ID or cell index maybe assigned to a cell. A cell ID may be determined using asynchronization signal transmitted on a downlink carrier. A cell indexmay be determined using RRC messages. For example, when thespecification refers to a first physical cell ID for a first downlinkcarrier, the specification may mean the first physical cell ID is for acell comprising the first downlink carrier. The same concept may applyto, for example, carrier activation. When the specification indicatesthat a first carrier is activated, the specification may equally meanthat the cell comprising the first carrier is activated.

Embodiments may be configured to operate as needed. The disclosedmechanism may be performed when certain criteria are met, for example,in a wireless device, a base station, a radio environment, a network, acombination of the above, and/or the like. Example criteria may bebased, at least in part, on for example, traffic load, initial systemset up, packet sizes, traffic characteristics, a combination of theabove, and/or the like. When the one or more criteria are met, variousexample embodiments may be applied. Therefore, it may be possible toimplement example embodiments that selectively implement disclosedprotocols.

A base station may communicate with a mix of wireless devices. Wirelessdevices may support multiple technologies, and/or multiple releases ofthe same technology. Wireless devices may have some specificcapability(ies) depending on its wireless device category and/orcapability(ies). A base station may comprise multiple sectors. When thisdisclosure refers to a base station communicating with a plurality ofwireless devices, this disclosure may refer to a subset of the totalwireless devices in a coverage area. This disclosure may refer to, forexample, a plurality of wireless devices of a given LTE release with agiven capability and in a given sector of the base station. Theplurality of wireless devices in this disclosure may refer to a selectedplurality of wireless devices, and/or a subset of total wireless devicesin a coverage area which perform according to disclosed methods, and/orthe like. There may be a plurality of wireless devices in a coveragearea that may not comply with the disclosed methods, for example,because those wireless devices perform based on older releases of LTEtechnology.

FIG. 6 and FIG. 7 are example diagrams for protocol structure with CAand DC as per an aspect of an embodiment of the present invention.E-UTRAN may support Dual Connectivity (DC) operation whereby a multipleRX/TX UE in RRC_CONNECTED may be configured to utilize radio resourcesprovided by two schedulers located in two eNBs connected via a non-idealbackhaul over the X2 interface. eNBs involved in DC for a certain UE mayassume two different roles: an eNB may either act as an MeNB or as anSeNB. In DC a UE may be connected to one MeNB and one SeNB. Mechanismsimplemented in DC may be extended to cover more than two eNBs. FIG. 7illustrates one example structure for the UE side MAC entities when aMaster Cell Group (MCG) and a Secondary Cell Group (SCG) are configured,and it may not restrict implementation. Media Broadcast MulticastService (MBMS) reception is not shown in this figure for simplicity.

In DC, the radio protocol architecture that a particular bearer uses maydepend on how the bearer is setup. Three alternatives may exist, an MCGbearer, an SCG bearer and a split bearer as shown in FIG. 6. RRC may belocated in MeNB and SRBs may be configured as a MCG bearer type and mayuse the radio resources of the MeNB. DC may also be described as havingat least one bearer configured to use radio resources provided by theSeNB. DC may or may not be configured/implemented in example embodimentsof the invention.

In the case of DC, the UE may be configured with two MAC entities: oneMAC entity for MeNB, and one MAC entity for SeNB. In DC, the configuredset of serving cells for a UE may comprise of two subsets: the MasterCell Group (MCG) containing the serving cells of the MeNB, and theSecondary Cell Group (SCG) containing the serving cells of the SeNB. Fora SCG, one or more of the following may be applied: at least one cell inthe SCG has a configured UL CC and one of them, named PSCell (or PCellof SCG, or sometimes called PCell), is configured with PUCCH resources;when the SCG is configured, there may be at least one SCG bearer or oneSplit bearer; upon detection of a physical layer problem or a randomaccess problem on a PSCell, or the maximum number of RLC retransmissionshas been reached associated with the SCG, or upon detection of an accessproblem on a PSCell during a SCG addition or a SCG change: a RRCconnection re-establishment procedure may not be triggered, ULtransmissions towards cells of the SCG are stopped, a MeNB may beinformed by the UE of a SCG failure type, for split bearer, the DL datatransfer over the MeNB is maintained; the RLC AM bearer may beconfigured for the split bearer; like PCell, PSCell may not bede-activated; PSCell may be changed with a SCG change (e.g. withsecurity key change and a RACH procedure); and/or neither a directbearer type change between a Split bearer and a SCG bearer norsimultaneous configuration of a SCG and a Split bearer are supported.

With respect to the interaction between a MeNB and a SeNB, one or moreof the following principles may be applied: the MeNB may maintain theRRM measurement configuration of the UE and may, (e.g, based on receivedmeasurement reports or traffic conditions or bearer types), decide toask a SeNB to provide additional resources (serving cells) for a UE;upon receiving a request from the MeNB, a SeNB may create a containerthat may result in the configuration of additional serving cells for theUE (or decide that it has no resource available to do so); for UEcapability coordination, the MeNB may provide (part of) the ASconfiguration and the UE capabilities to the SeNB; the MeNB and the SeNBmay exchange information about a UE configuration by employing of RRCcontainers (inter-node messages) carried in X2 messages; the SeNB mayinitiate a reconfiguration of its existing serving cells (e.g., PUCCHtowards the SeNB); the SeNB may decide which cell is the PSCell withinthe SCG; the MeNB may not change the content of the RRC configurationprovided by the SeNB; in the case of a SCG addition and a SCG SCelladdition, the MeNB may provide the latest measurement results for theSCG cell(s); both a MeNB and a SeNB may know the SFN and subframe offsetof each other by OAM, (e.g., for the purpose of DRX alignment andidentification of a measurement gap). In an example, when adding a newSCG SCell, dedicated RRC signalling may be used for sending requiredsystem information of the cell as for CA, except for the SFN acquiredfrom a MIB of the PSCell of a SCG.

According to some of the various aspects of embodiments, serving cellshaving an uplink to which the same time alignment (TA) applies may begrouped in a TA group (TAG). Serving cells in one TAG may use the sametiming reference. For a given TAG, user equipment (UE) may use onedownlink carrier as a timing reference at a given time. The UE may use adownlink carrier in a TAG as a timing reference for that TAG. For agiven TAG, a UE may synchronize uplink subframe and frame transmissiontiming of uplink carriers belonging to the same TAG. According to someof the various aspects of embodiments, serving cells having an uplink towhich the same TA applies may correspond to serving cells hosted by thesame receiver. A TA group may comprise at least one serving cell with aconfigured uplink. A UE supporting multiple TAs may support two or moreTA groups. One TA group may contain the PCell and may be called aprimary TAG (pTAG). In a multiple TAG configuration, at least one TAgroup may not contain the PCell and may be called a secondary TAG(sTAG). Carriers within the same TA group may use the same TA value andthe same timing reference. When DC is configured, cells belonging to acell group (MCG or SCG) may be grouped into multiple TAGs including apTAG and one or more sTAGs.

FIG. 8 shows example TAG configurations as per an aspect of anembodiment of the present invention. In Example 1, pTAG comprises PCell,and an sTAG comprises SCell1. In Example 2, a pTAG comprises a PCell andSCell1, and an sTAG comprises SCell2 and SCell3. In Example 3, pTAGcomprises PCell and SCell1, and an sTAG1 includes SCell2 and SCell3, andsTAG2 comprises SCell4. Up to four TAGs may be supported in a cell group(MCG or SCG) and other example TAG configurations may also be provided.In various examples in this disclosure, example mechanisms are describedfor a pTAG and an sTAG. The operation with one example sTAG isdescribed, and the same operation may be applicable to other sTAGs. Theexample mechanisms may be applied to configurations with multiple sTAGs.

According to some of the various aspects of embodiments, TA maintenance,pathloss reference handling and a timing reference for a pTAG may followLTE release 10 principles in the MCG and/or SCG. The UE may need tomeasure downlink pathloss to calculate uplink transmit power. A pathlossreference may be used for uplink power control and/or transmission ofrandom access preamble(s). UE may measure downlink pathloss usingsignals received on a pathloss reference cell. For SCell(s) in a pTAG,the choice of a pathloss reference for cells may be selected from and/orbe limited to the following two options: a) the downlink SCell linked toan uplink SCell using system information block 2 (SIB2), and b) thedownlink pCell. The pathloss reference for SCells in a pTAG may beconfigurable using RRC message(s) as a part of an SCell initialconfiguration and/or reconfiguration. According to some of the variousaspects of embodiments, a PhysicalConfigDedicatedSCell informationelement (IE) of an SCell configuration may include a pathloss referenceSCell (downlink carrier) for an SCell in a pTAG. The downlink SCelllinked to an uplink SCell using system information block 2 (SIB2) may bereferred to as the SIB2 linked downlink of the SCell. Different TAGs mayoperate in different bands. For an uplink carrier in an sTAG, thepathloss reference may be only configurable to the downlink SCell linkedto an uplink SCell using the system information block 2 (SIB2) of theSCell.

To obtain initial uplink (UL) time alignment for an sTAG, an eNB mayinitiate an RA procedure. In an sTAG, a UE may use one of any activatedSCells from this sTAG as a timing reference cell. In an exampleembodiment, the timing reference for SCells in an sTAG may be the SIB2linked downlink of the SCell on which the preamble for the latest RAprocedure was sent. There may be one timing reference and one timealignment timer (TAT) per TA group. A TAT for TAGs may be configuredwith different values. In a MAC entity, when a TAT associated with apTAG expires: all TATs may be considered as expired, the UE may flushHARQ buffers of serving cells, the UE may clear any configured downlinkassignment/uplink grants, and the RRC in the UE may release PUCCH/SRSfor all configured serving cells. When the pTAG TAT is not running, ansTAG TAT may not be running. When the TAT associated with an sTAGexpires: a) SRS transmissions may be stopped on the correspondingSCells, b) SRS RRC configuration may be released, c) CSI reportingconfiguration for corresponding SCells may be maintained, and/or d) theMAC in the UE may flush the uplink HARQ buffers of the correspondingSCells.

An eNB may initiate an RA procedure via a PDCCH order for an activatedSCell. This PDCCH order may be sent on a scheduling cell of this SCell.When cross carrier scheduling is configured for a cell, the schedulingcell may be different than the cell that is employed for preambletransmission, and the PDCCH order may include an SCell index. At least anon-contention based RA procedure may be supported for SCell(s) assignedto sTAG(s).

FIG. 9 is an example message flow in a random access process in asecondary TAG as per an aspect of an embodiment of the presentinvention. An eNB transmits an activation command 600 to activate anSCell. A preamble 602 (Msg1) may be sent by a UE in response to a PDCCHorder 601 on an SCell belonging to an sTAG. In an example embodiment,preamble transmission for SCells may be controlled by the network usingPDCCH format 1A. Msg2 message 603 (RAR: random access response) inresponse to the preamble transmission on the SCell may be addressed toRA-RNTI in a PCell common search space (CSS). Uplink packets 604 may betransmitted on the SCell in which the preamble was transmitted.

According to some of the various aspects of embodiments, initial timingalignment may be achieved through a random access procedure. This mayinvolve a UE transmitting a random access preamble and an eNB respondingwith an initial TA command NTA (amount of timing advance) within arandom access response window. The start of the random access preamblemay be aligned with the start of a corresponding uplink subframe at theUE assuming NTA=0. The eNB may estimate the uplink timing from therandom access preamble transmitted by the UE. The TA command may bederived by the eNB based on the estimation of the difference between thedesired UL timing and the actual UL timing. The UE may determine theinitial uplink transmission timing relative to the correspondingdownlink of the sTAG on which the preamble is transmitted.

The mapping of a serving cell to a TAG may be configured by a servingeNB with RRC signaling. The mechanism for TAG configuration andreconfiguration may be based on RRC signaling. According to some of thevarious aspects of embodiments, when an eNB performs an SCell additionconfiguration, the related TAG configuration may be configured for theSCell. In an example embodiment, an eNB may modify the TAG configurationof an SCell by removing (releasing) the SCell and adding(configuring) anew SCell (with the same physical cell ID and frequency) with an updatedTAG ID. The new SCell with the updated TAG ID may initially be inactivesubsequent to being assigned the updated TAG ID. The eNB may activatethe updated new SCell and start scheduling packets on the activatedSCell. In an example implementation, it may not be possible to changethe TAG associated with an SCell, but rather, the SCell may need to beremoved and a new SCell may need to be added with another TAG. Forexample, if there is a need to move an SCell from an sTAG to a pTAG, atleast one RRC message, for example, at least one RRC reconfigurationmessage, may be send to the UE to reconfigure TAG configurations byreleasing the SCell and then configuring the SCell as a part of the pTAG(when an SCell is added/configured without a TAG index, the SCell may beexplicitly assigned to the pTAG). The PCell may not change its TA groupand may always be a member of the pTAG.

The purpose of an RRC connection reconfiguration procedure may be tomodify an RRC connection, (e.g. to establish, modify and/or release RBs,to perform handover, to setup, modify, and/or release measurements, toadd, modify, and/or release SCells). If the received RRC ConnectionReconfiguration message includes the sCellToReleaseList, the UE mayperform an SCell release. If the received RRC Connection Reconfigurationmessage includes the sCellToAddModList, the UE may perform SCelladditions or modification.

In LTE Release-10 and Release-11 CA, a PUCCH is only transmitted on thePCell (PSCell) to an eNB. In LTE-Release 12 and earlier, a UE maytransmit PUCCH information on one cell (PCell or PSCell) to a given eNB.

As the number of CA capable UEs and also the number of aggregatedcarriers increase, the number of PUCCHs and also the PUCCH payload sizemay increase. Accommodating the PUCCH transmissions on the PCell maylead to a high PUCCH load on the PCell. A PUCCH on an SCell may beintroduced to offload the PUCCH resource from the PCell. More than onePUCCH may be configured for example, a PUCCH on a PCell and anotherPUCCH on an SCell. FIG. 10 is an example grouping of cells into PUCCHgroups as per an aspect of an embodiment of the present invention. Inthe example embodiments, one, two or more cells may be configured withPUCCH resources for transmitting CSI/ACK/NACK to a base station. Cellsmay be grouped into multiple PUCCH groups, and one or more cell within agroup may be configured with a PUCCH. In an example configuration, oneSCell may belong to one PUCCH group. SCells with a configured PUCCHtransmitted to a base station may be called a PUCCH SCell, and a cellgroup with a common PUCCH resource transmitted to the same base stationmay be called a PUCCH group.

In Release-12, a PUCCH can be configured on a PCell and/or a PSCell, butcannot be configured on other SCells. In an example embodiment, a UE maytransmit a message indicating that the UE supports PUCCH configurationon a PCell and SCell. Such an indication may be separate from anindication of dual connectivity support by the UE. In an exampleembodiment, a UE may support both DC and PUCCH groups. In an exampleembodiment, either DC or PUCCH groups may be configured, but not both.In another example embodiment, more complicated configurationscomprising both DC and PUCCH groups may be supported.

When a UE is capable of configuring PUCCH groups, and if a UE indicatesthat it supports simultaneous PUCCH/PUSCH transmission capability, itmay imply that the UE supports simultaneous PUCCH/PUSCH transmission onboth PCell and SCell. When multiple PUCCH groups are configured, a PUCCHmay be configured or not configured with simultaneous PUCCH/PUSCHtransmission.

In an example embodiment, PUCCH transmission to a base station on twoserving cells may be realized as shown in FIG. 10. A first group ofcells may employ a PUCCH on the PCell and may be called PUCCH group 1 ora primary PUCCH group. A second group of cells may employ a PUCCH on anSCell and may be called PUCCH group 2 or a secondary PUCCH group. One,two or more PUCCH groups may be configured. In an example, cells may begrouped into two PUCCH groups, and each PUCCH group may include a cellwith PUCCH resources. A PCell may provide PUCCH resources for theprimary PUCCH group and an SCell in the secondary PUCCH group mayprovide PUCCH resources for the cells in the secondary PUCCH group. Inan example embodiment, no cross-carrier scheduling between cells indifferent PUCCH groups may be configured. When cross-carrier schedulingbetween cells in different PUCCH groups is not configured, ACK/NACK onPHICH channel may be limited within a PUCCH group. Both downlink anduplink scheduling activity may be separate between cells belonging todifferent PUCCH groups.

A PUCCH on an SCell may carry HARQ-ACK and CSI information. A PCell maybe configured with PUCCH resources. In an example embodiment, RRCparameters for an SCell PUCCH Power Control for a PUCCH on an SCell maybe different from those of a PCell PUCCH. A Transmit Power Controlcommand for a PUCCH on an SCell may be transmitted in DCI(s) on theSCell carrying the PUCCH.

UE procedures on a PUCCH transmission may be different and/orindependent between PUCCH groups. For example, determination of DLHARQ-ACK timing, PUCCH resource determination for HARQ-ACK and/or CSI,Higher-layer configuration of simultaneous HARQ-ACK+CSI on a PUCCH,Higher-layer configuration of simultaneous HARQ-ACK+SRS in one subframemay be configured differently for a PUCCH PCell and a PUCCH SCell.

A PUCCH group may be a group of serving cells configured by a RRC anduse the same serving cell in the group for transmission of a PUCCH. APrimary PUCCH group may be a PUCCH group containing a PCell. A secondaryPUCCH group may be a PUCCH cell group not containing the PCell. In anexample embodiment, an SCell may belong to one PUCCH group. When oneSCell belongs to a PUCCH group, ACK/NACK or CSI for that SCell may betransmitted over the PUCCH in that PUCCH group (over PUCCH SCell orPUCCH PCell). A PUCCH on an SCell may reduce the PUCCH load on thePCell. A PUCCH SCell may be employed for UCI transmission of SCells inthe corresponding PUCCH group.

In an example embodiment, a flexible PUCCH configuration in whichcontrol signalling is sent on one, two or more PUCCHs may be possible.Beside the PCell, it may be possible to configure a selected number ofSCells for PUCCH transmission (herein called PUCCH SCells). Controlsignalling information conveyed in a certain PUCCH SCell may be relatedto a set of SCells in a corresponding PUCCH group that are configured bythe network via RRC signalling.

PUCCH control signalling carried by a PUCCH channel may be distributedbetween a PCell and SCells for off-loading or robustness purposes. Byenabling a PUCCH in an SCell, it may be possible to distribute theoverall CSI reports for a given UE between a PCell and a selected numberof SCells (e.g. PUCCH SCells), thereby limiting PUCCH CSI resourceconsumption by a given UE on a certain cell. It may be possible to mapCSI reports for a certain SCell to a selected PUCCH SCell. An SCell maybe assigned a certain periodicity and time-offset for transmission ofcontrol information. Periodic CSI for a serving cell may be mapped on aPUCCH (on the PCell or on a PUCCH-SCell) via RRC signalling. Thepossibility of distributing CSI reports, HARQ feedbacks, and/orScheduling Requests across PUCCH SCells may provide flexibility andcapacity improvements. HARQ feedback for a serving cell may be mapped ona PUCCH (on the PCell or on a PUCCH SCell) via RRC signalling.

In example embodiments, PUCCH transmission may be configured on a PCell,as well as one SCell in CA. An SCell PUCCH may be realized using theconcept of PUCCH groups, where aggregated cells are grouped into two ormore PUCCH groups. One cell from a PUCCH group may be configured tocarry a PUCCH. More than 5 carriers may be configured. In the exampleembodiments, up to n carriers may be aggregated. For example, n may be16, 32, or 64. Some CCs may have non-backward compatible configurationssupporting only advanced UEs (e.g. support licensed assisted accessSCells). In an example embodiment, one SCell PUCCH (e.g. two PUCCHgroups) may be supported. In another example embodiment, a PUCCH groupconcept with multiple (more than one) SCells carrying PUCCH may beemployed (e.g., there can be more than two PUCCH groups).

In an example embodiment, a given PUCCH group may not comprise servingcells of both MCG and SCG. One of the PUCCHs may be configured on thePCell. In an example embodiment, PUCCH mapping of serving cells may beconfigured by RRC messages. In an example embodiment, a maximum value ofan SCellIndex and a ServCellIndex may be 31 (ranging from 0 to 31). Inan example, a maximum value of stag-Id may be 3. The CIF for a scheduledcell may be configured explicitly. A PUCCH SCell may be configured bygiving a PUCCH configuration for an SCell. A HARQ feedback and CSIreport of a PUCCH SCell may be sent on the PUCCH of that PUCCH SCell.The HARQ feedback and CSI report of a SCell may sent on a PUCCH of aPCell if no PUCCH SCell is signalled for that SCell. The HARQ feedbackand CSI report of an SCell may be sent on the PUCCH of one PUCCH SCell;hence they may not be sent on the PUCCH of different PUCCH SCell. The UEmay report a Type 2 PH for serving cells configured with a PUCCH. In anexample embodiment, a MAC activation/deactivation may be supported for aPUCCH SCell. An eNB may manage the activation/deactivation status forSCells. A newly added PUCCH SCell may be initially deactivated.

In an example embodiment, independent configuration of PUCCH groups andTAGs may be supported. FIG. 11 and FIG. 12 show example configurationsof TAGs and PUCCH groups. For example, one TAG may contain multipleserving cells with a PUCCH. For example, each TAG may only comprisecells of one PUCCH group. For example, a TAG may comprise the servingcells (without a PUCCH) which belong to different PUCCH groups.

There may not be a one-to-one mapping between TAGs and PUCCH groups. Forexample, in a configuration, a PUCCH SCell may belong to primary TAG. Inan example implementation, the serving cells of one PUCCH group may bein different TAGs and serving cells of one TAG may be in different PUCCHgroups. Configuration of PUCCH groups and TAGs may be left to eNBimplementation. In another example implementation, restriction(s) on theconfiguration of a PUCCH cell may be specified. For example, in anexample embodiment, cells in a given PUCCH group may belong to the sameTAG. In an example, an sTAG may only comprise cells of one PUCCH group.In an example, one-to-one mapping between TAGs and PUCCH groups may beimplemented. In implementation, cell configurations may be limited tosome of the examples. In other implementations, some or all the belowconfigurations may be allowed.

In an example embodiment, for an SCell in a pTAG, the timing referencemay be a PCell. For an SCell in an sTAG, the timing reference may be anyactivated SCell in the sTAG. For an SCell (configured with PUCCH or not)in a pTAG, a pathloss reference may be configured to be a PCell or anSIB-2 linked SCell. For an SCell in a sTAG, the pathloss reference maybe the SIB-2 linked SCell. When a TAT associated with a pTAG is expired,the TAT associated with sTAGs may be considered as expired. When a TATof an sTAG containing PUCCH SCell expires, the MAC may indicate to anRRC to release PUCCH resource for the PUCCH group. When the TAT of ansTAG containing a PUCCH SCell is not running, the uplink transmission(PUSCH) for SCells in the secondary PUCCH group not belonging to thesTAG including the PUCCH SCell may not be impacted. The TAT expiry of ansTAG containing a PUCCH SCell may not trigger TAT expiry of other TAGsto which other SCells in the same PUCCH group belong. When the TATassociated with sTAG not containing a PUCCH SCell is not running, thewireless device may stop the uplink transmission for the SCell in thesTAG and may not impact other TAGs.

In an example embodiment, a MAC entity may have a configurable timertimeAlignmentTimer per TAG. The timeAlignmentTimer may be used tocontrol how long the MAC entity considers the Serving Cells belonging tothe associated TAG to be uplink time aligned. The MAC entity may, when aTiming Advance Command MAC control element is received, apply the TimingAdvance Command for the indicated TAG; start or restart thetimeAlignmentTimer associated with the indicated TAG. The MAC entitymay, when a Timing Advance Command is received in a Random AccessResponse message for a serving cell belonging to a TAG and/or if theRandom Access Preamble was not selected by the MAC entity, apply theTiming Advance Command for this TAG and start or restart thetimeAlignmentTimer associated with this TAG. Otherwise, if thetimeAlignmentTimer associated with this TAG is not running, the TimingAdvance Command for this TAG may be applied and the timeAlignmentTimerassociated with this TAG started. When the contention resolution isconsidered not successful, a timeAlignmentTimer associated with this TAGmay be stopped. Otherwise, the MAC entity may ignore the received TimingAdvance Command.

Example embodiments of the invention may enable operation of multiplePUCCH groups. Other example embodiments may comprise a non-transitorytangible computer readable media comprising instructions executable byone or more processors to cause operation of PUCCH groups. Yet otherexample embodiments may comprise an article of manufacture thatcomprises a non-transitory tangible computer readable machine-accessiblemedium having instructions encoded thereon for enabling programmablehardware to cause a device (e.g. wireless communicator, UE, basestation, etc.) to enable operation of PUCCH groups. The device mayinclude processors, memory, interfaces, and/or the like. Other exampleembodiments may comprise communication networks comprising devices suchas base stations, wireless devices (or user equipment: UE), servers,switches, antennas, and/or the like. In an example embodiment one ormore TAGs may be configured along with PUCCH group configuration.

FIG. 13 is an example MAC PDU as per an aspect of an embodiment of thepresent invention. In an example embodiment, a MAC PDU may comprise of aMAC header, zero or more MAC Service Data Units (MAC SDU), zero or moreMAC control elements, and optionally padding. The MAC header and the MACSDUs may be of variable sizes. A MAC PDU header may comprise one or moreMAC PDU subheaders. A subheader may correspond to either a MAC SDU, aMAC control element or padding. A MAC PDU subheader may comprise headerfields R, F2, E, LCID, F, and/or L. The last subheader in the MAC PDUand subheaders for fixed sized MAC control elements may comprise thefour header fields R, F2, E, and/or LCID. A MAC PDU subheadercorresponding to padding may comprise the four header fields R, F2, E,and/or LCID.

In an example embodiment, LCID or Logical Channel ID field may identifythe logical channel instance of the corresponding MAC SDU or the type ofthe corresponding MAC control element or padding. There may be one LCIDfield for a MAC SDU, MAC control element or padding included in the MACPDU. In addition to that, one or two additional LCID fields may beincluded in the MAC PDU when single-byte or two-byte padding is requiredbut cannot be achieved by padding at the end of the MAC PDU. The LCIDfield size may be, e.g. 5 bits. L or the Length field may indicate thelength of the corresponding MAC SDU or variable-sized MAC controlelement in bytes. There may be one L field per MAC PDU subheader exceptfor the last subheader and subheaders corresponding to fixed-sized MACcontrol elements. The size of the L field may be indicated by the Ffield and F2 field. The F or the Format field may indicate the size ofthe Length field. There may be one F field per MAC PDU subheader exceptfor the last subheader and subheaders corresponding to fixed-sized MACcontrol elements and expect for when F2 is set to 1. The size of the Ffield may be 1 bit. In an example, if the F field is included, and/or ifthe size of the MAC SDU or variable-sized MAC control element is lessthan 128 bytes, the value of the F field is set to 0, otherwise it isset to 1. The F2 or the Format2 field may indicate the size of theLength field. There may be one F2 field per MAC PDU subheader. The sizeof the F2 field may be 1 bit. In an example, if the size of the MAC SDUor variable-sized MAC control element is larger than 32767 bytes and ifthe corresponding subheader is not the last subheader, the value of theF2 field may be set to 1, otherwise it is set to 0. The E or theExtension field may be a flag indicating if more fields are present inthe MAC header or not. The E field may be set to “1” to indicate anotherset of at least R/F2/E/LCID fields. The E field may be set to “0” toindicate that either a MAC SDU, a MAC control element or padding startsat the next byte. R or reserved bit, set to “0”.

MAC PDU subheaders may have the same order as the corresponding MACSDUs, MAC control elements and padding. MAC control elements may beplaced before any MAC SDU. Padding may occur at the end of the MAC PDU,except when single-byte or two-byte padding is required. Padding mayhave any value and the MAC entity may ignore it. When padding isperformed at the end of the MAC PDU, zero or more padding bytes may beallowed. When single-byte or two-byte padding is required, one or twoMAC PDU subheaders corresponding to padding may be placed at thebeginning of the MAC PDU before any other MAC PDU subheader. In anexample, a maximum of one MAC PDU may be transmitted per TB per MACentity, a maximum of one MCH MAC PDU can be transmitted per TTI.

At least one RRC message may provide configuration parameters for atleast one cell and configuration parameters for PUCCH groups. Theinformation elements in one or more RRC messages may provide mappingbetween configured cells and PUCCH SCells. Cells may be grouped into aplurality of cell groups and a cell may be assigned to one of theconfigured PUCCH groups. There may be a one-to-one relationship betweenPUCCH groups and cells with configured PUCCH resources. At least one RRCmessage may provide mapping between an SCell and a PUCCH group, andPUCCH configuration on PUCCH SCell.

System information (common parameters) for an SCell may be carried in aRadioResourceConfigCommonSCell in a dedicated RRC message. Some of thePUCCH related information may be included in common information of anSCell (e.g. in the RadioResourceConfigCommonSCell). Dedicatedconfiguration parameters of SCell and PUCCH resources may be configuredby dedicated RRC signaling using, for example,RadioResourceConfigDedicatedSCell.

The IE PUCCH-ConfigCommon and IE PUCCH-ConfigDedicated may be used tospecify the common and the UE specific PUCCH configuration respectively.

In an example, PUCCH-ConfigCommon may include: deltaPUCCH-Shift:ENUMERATED {ds1, ds2, ds3}; nRB-CQI: INTEGER (0 . . . 98); nCS-AN:INTEGER (0 . . . 7); and/or n1PUCCH-AN: INTEGER (0 . . . 2047). Theparameter deltaPUCCH-Shift (Δ_(shift) ^(PUCCH)), nRB-CQI (N_(RB) ⁽²⁾),nCS-An (N_(cs) ⁽¹⁾) and n1PUCCH-AN (N_(PUCCH) ⁽¹⁾) may be physical layerparameters of PUCCH.

PUCCH-ConfigDedicated may be employed. PUCCH-ConfigDedicated mayinclude: ackNackRepetition CHOICE{release: NULL, setup: SEQUENCE{repetitionFactor: ENUMERATED {n2, n4, n6, spare1}, n1PUCCH-AN-Rep:INTEGER (0 . . . 2047)}}, tdd-AckNackFeedbackMode: ENUMERATED {bundling,multiplexing} OPTIONAL}. ackNackRepetitionj parameter indicates whetherACK/NACK repetition is configured. n2 corresponds to repetition factor2, n4 to 4 for repetitionFactor parameter (N_(ANRep)). n1PUCCH-AN-Repparameter may be n_(PUCCH, ANRep) ^((1,p)) for antenna port P0 and forantenna port P1. dd-AckNackFeedbackMode parameter may indicate one ofthe TDD ACK/NACK feedback modes used. The value bundling may correspondto use of ACK/NACK bundling whereas, the value multiplexing maycorrespond to ACK/NACK multiplexing. The same value may apply to bothACK/NACK feedback modes on PUCCH as well as on PUSCH.

The parameter PUCCH-ConfigDedicated may include simultaneous PUCCH-PUSCHparameter indicating whether simultaneous PUCCH and PUSCH transmissionsis configured. An E-UTRAN may configure this field for the PCell whenthe nonContiguousUL-RA-WithinCC-Info is set to supported in the band onwhich PCell is configured. The E-UTRAN may configure this field for thePSCell when the nonContiguousUL-RA-WithinCC-Info is set to supported inthe band on which PSCell is configured. The E-UTRAN may configure thisfield for the PUCCH SCell when the nonContiguousUL-RA-WithinCC-Info isset to supported in the band on which PUCCH SCell is configured.

A UE may transmit radio capabilities to an eNB to indicate whether UEsupport the configuration of PUCCH groups. The simultaneous PUCCH-PUSCHin the UE capability message may be applied to both a PCell and anSCell. Simultaneous PUCCH+PUSCH may be configured separately (usingseparate IEs) for a PCell and a PUCCH SCell. For example, a PCell and aPUCCH SCell may have different or the same configurations related tosimultaneous PUCCH+PUSCH.

The eNB may select the PUCCH SCell among current SCells or candidateSCells considering cell loading, carrier quality (e.g. using measurementreports), carrier configuration, and/or other parameters. From afunctionality perspective, a PUCCH Cell group management procedure mayinclude a PUCCH Cell group addition, a PUCCH cell group release, a PUCCHcell group change and/or a PUCCH cell group reconfiguration. The PUCCHcell group addition procedure may be used to add a secondary PUCCH cellgroup (e.g., to add PUCCH SCell and one or more SCells in the secondaryPUCCH cell group). In an example embodiment, cells may be released andadded employing one or more RRC messages. In another example embodiment,cells may be released employing a first RRC message and then addedemploying a second RRC messages.

SCells including PUCCH SCell may be in a deactivated state when they areconfigured. A PUCCH SCell may be activated after an RRC configurationprocedure by an activation MAC CE. An eNB may transmit a MAC CEactivation command to a UE. The UE may activate an SCell in response toreceiving the MAC CE activation command

In example embodiments, a timer is running once it is started, until itis stopped or until it expires; otherwise it may not be running A timercan be started if it is not running or restarted if it is running. Forexample, a timer may be started or restarted from its initial value.

The amount of data traffic carried over cellular networks is expected toincrease for many years to come. The number of users/devices isincreasing and each user/device accesses an increasing number andvariety of services, e.g. video delivery, large files, images. Thisrequires not only high capacity in the network, but also provisioningvery high data rates to meet customers' expectations on interactivityand responsiveness. More spectrum is therefore needed for cellularoperators to meet the increasing demand Considering user expectations ofhigh data rates along with seamless mobility, it is beneficial that morespectrum be made available for deploying macro cells as well as smallcells for cellular systems.

Striving to meet the market demands, there has been increasing interestfrom operators in deploying some complementary access utilizingunlicensed spectrum to meet the traffic growth. This is exemplified bythe large number of operator-deployed Wi-Fi networks and the 3GPPstandardization of LTE/WLAN interworking solutions. This interestindicates that unlicensed spectrum, when present, can be an effectivecomplement to licensed spectrum for cellular operators to helpaddressing the traffic explosion in some scenarios, such as hotspotareas. LAA offers an alternative for operators to make use of unlicensedspectrum while managing one radio network, thus offering newpossibilities for optimizing the network's efficiency.

In an example embodiment, Listen-before-talk (clear channel assessment)may be implemented for transmission in an LAA cell. In alisten-before-talk (LBT) procedure, equipment may apply a clear channelassessment (CCA) check before using the channel. For example, the CCAutilizes at least energy detection to determine the presence or absenceof other signals on a channel in order to determine if a channel isoccupied or clear, respectively. For example, European and Japaneseregulations mandate the usage of LBT in the unlicensed bands. Apart fromregulatory requirements, carrier sensing via LBT may be one way for fairsharing of the unlicensed spectrum.

In an example embodiment, discontinuous transmission on an unlicensedcarrier with limited maximum transmission duration may be enabled. Someof these functions may be supported by one or more signals to betransmitted from the beginning of a discontinuous LAA downlinktransmission Channel reservation may be enabled by the transmission ofsignals, by an LAA node, after gaining channel access via a successfulLBT operation, so that other nodes that receive the transmitted signalwith energy above a certain threshold sense the channel to be occupied.Functions that may need to be supported by one or more signals for LAAoperation with discontinuous downlink transmission may include one ormore of the following: detection of the LAA downlink transmission(including cell identification) by UEs; time & frequency synchronizationof UEs.

In an example embodiment, DL LAA design may employ subframe boundaryalignment according to LTE-A carrier aggregation timing relationshipsacross serving cells aggregated by CA. This may not imply that the eNBtransmissions can start only at the subframe boundary. LAA may supporttransmitting PDSCH when not all OFDM symbols are available fortransmission in a subframe according to LBT. Delivery of necessarycontrol information for the PDSCH may also be supported.

LBT procedure may be employed for fair and friendly coexistence of LAAwith other operators and technologies operating in unlicensed spectrum.LBT procedures on a node attempting to transmit on a carrier inunlicensed spectrum require the node to perform a clear channelassessment to determine if the channel is free for use. An LBT proceduremay involve at least energy detection to determine if the channel isbeing used. For example, regulatory requirements in some regions, e.g.,in Europe, specify an energy detection threshold such that if a nodereceives energy greater than this threshold, the node assumes that thechannel is not free. While nodes may follow such regulatoryrequirements, a node may optionally use a lower threshold for energydetection than that specified by regulatory requirements. In an example,LAA may employ a mechanism to adaptively change the energy detectionthreshold, e.g., LAA may employ a mechanism to adaptively lower theenergy detection threshold from an upper bound. Adaptation mechanism maynot preclude static or semi-static setting of the threshold. In anexample Category 4 LBT mechanism or other type of LBT mechanisms may beimplemented.

Various example LBT mechanisms may be implemented. In an example, forsome signals, in some implementation scenarios, in some situations,and/or in some frequencies no LBT procedure may performed by thetransmitting entity. In an example, Category 2 (e.g. LBT without randomback-off) may be implemented. The duration of time that the channel issensed to be idle before the transmitting entity transmits may bedeterministic. In an example, Category 3 (e.g. LBT with random back-offwith a contention window of fixed size) may be implemented. The LBTprocedure may have the following procedure as one of its components. Thetransmitting entity may draw a random number N within a contentionwindow. The size of the contention window may be specified by theminimum and maximum value of N. The size of the contention window may befixed. The random number N may be employed in the LBT procedure todetermine the duration of time that the channel is sensed to be idlebefore the transmitting entity transmits on the channel. In an example,Category 4 (e.g. LBT with random back-off with a contention window ofvariable size) may be implemented. The transmitting entity may draw arandom number N within a contention window. The size of contentionwindow may be specified by the minimum and maximum value of N. Thetransmitting entity may vary the size of the contention window whendrawing the random number N. The random number N is used in the LBTprocedure to determine the duration of time that the channel is sensedto be idle before the transmitting entity transmits on the channel

LAA may employ uplink LBT at the UE. The UL LBT scheme may be differentfrom the DL LBT scheme (e.g. by using different LBT mechanisms orparameters) for example, since the LAA UL is based on scheduled accesswhich affects a UE's channel contention opportunities. Otherconsiderations motivating a different UL LBT scheme include, but are notlimited to, multiplexing of multiple UEs in a single subframe.

In an example, a DL transmission burst may be a continuous transmissionfrom a DL transmitting node with no transmission immediately before orafter from the same node on the same CC. An UL transmission burst from aUE perspective may be a continuous transmission from a UE with notransmission immediately before or after from the same UE on the sameCC. In an example, UL transmission burst is defined from a UEperspective. In an example, an UL transmission burst may be defined froman eNB perspective. In an example, in case of an eNB operating DL+UL LAAover the same unlicensed carrier, DL transmission burst(s) and ULtransmission burst(s) on LAA may be scheduled in a TDM manner over thesame unlicensed carrier. For example, an instant in time may be part ofa DL transmission burst or an UL transmission burst.

3GPP TR 36.889 V1.0.1 (2015-06) is a Technical Report published by 3rdGeneration Partnership Project, in Technical Specification Group RadioAccess Network. 3GPP TR 36.889 is entitled “Study on Licensed-AssistedAccess to Unlicensed Spectrum”. The purpose of the TR is to document theidentified LTE enhancements and corresponding evaluations for a singleglobal solution framework for licensed-assisted access (LAA) tounlicensed spectrum.

3GPP TR 36.889 describes that contention based RA (random access) maynot be supported in cells operating in unlicensed bands (LAA cells).Contention free random access may be supported on LAA cells if the eNBdecides that RA is needed. If a UE is required to perform LBT (Listenbefore talk) before UL transmission, the handling of preambletransmission dropping from Rel-12 Dual Connectivity may be used asbaseline for preamble dropping on LAA carriers due to LBT failure.

In some example configurations, random access mechanism may not besupported on LAA cells. LAA cells may be small and hence there may notbe a need to initiate a RA for uplink synchronization. In some examplescenarios, cell radius may be relatively large and random access may beneeded. For example, in the lower 5 GHz band there may be a band (e.g.US UNII-1) which may allow up to 4 W EIRP (which may include the antennagain). And in this band the cells may be relatively large and hencerandom access may be needed. In an example embodiment, the eNB maydecide whether to perform a random access procedure on a cell or whetherto skip the random access procedure. The cell may be an LAA cell or alicensed cell.

Implementation of the preamble transmission dropping from Rel-12 DualConnectivity for preamble dropping on LAA carriers may result in manyimplementation issues. The behaviors of LAA cells may be unpredictableand implementation of preamble dropping (from Rel-12 Dual Connectivity)in LAA carriers may result in unpredictable results and/or inefficientbehaviors in a UE and/or an eNB. There is a need to further improve theUE and/or eNB behavior and improve the random access mechanism for LAAcarriers.

In carrier aggregation, a TAG is used to group cells with the sameuplink timing. Different TAGs may have different uplink timings. Theconcept of multiple TAGs may apply when cells in licensed spectrum aredeployed. The concept of multiple TAGs may also apply when LAA cells aredeployed. In an example embodiment, one or more LAA cells may have acommon uplink timing and may be grouped in a TAG. In an exampleembodiment, one or more LAA cells and one or more licensed cells may begrouped in a TAG depending on the uplink timings. In an exampleembodiment, licensed cells may be grouped in a TAG depending on uplinktimings. In an example deployment scenario, an LAA SCell and a licensedPCell may belong to different timing advance groups (TAGs), for exampletheir antennas may be located on different locations.

Contention free random access may be supported on an LAA SCell toestablish uplink synchronization. Random access on an sCell may beinitiated with a PDCCH order transmitted by an eNB to a UE. A PDCCHorder initiated random access may be supported for an LAA cell. In a RAprocedure initiated by PDCCH order on an LAA cell, issues with preambletransmission may be addressed. The Random Access Response (RAR) may besent on the PCell in carrier aggregation. The RAR (random accessresponse) may be received on a PCell. The PCell may be on a licensedcarrier.

In an example embodiment, a UE may not transmit any uplink data and/orsignal on an LAA cell if the LAA cell is occupied by other transmitters.Transmissions on an LAA carrier may be subject to LBT requirement and itmay be possible that a UE may not be able to perform the dedicatedpreamble transmission on a PRACH resource opportunity due tounavailability of the channel A UE may drop transmission of a dedicatedpreamble on a PRACH opportunity of an LAA SCell due to LBT requirement(when LBT fails). The random access preamble (RAP) transmission may bedropped in the PHY layer when a MAC layer requests for transmission ofthe RAP (random access preamble), if LBT process fails.

A UE may calculate the power ramping for preambles. In DC, dropping apreamble may not cause additional power ramping, e.g. the UE may notramp the preamble transmission power when the previous preamble wasdropped. The UE may ramp up the power when the preamble is actuallytransmitted, but not when a preamble is dropped. In DC, the PHY layermay drop RAP transmission in case the UE is power limited. In such ascenario, the PHY may inform the MAC layer of a RAP drop andaccordingly, MAC may not increase RA preamble transmission counter andRA preamble transmission power. If the PHY layer in a UE drops the PRACHtransmission, the PHY layer may send power ramping suspension indicatorto the higher layers (e.g. MAC layer).

In an example embodiment, a wireless device may receive from an eNB aPDCCH order initiating a random access procedure on an LAA cell. Thewireless device may start preamble transmission counter at 1. Preambletransmission counter may be for a number of physical layer transmissionsof the preamble. In a MAC entity if the notification of power rampingsuspension has not been received from lower layers (e.g. PHY layer), theMAC entity may increment preamble transmission counter by 1, otherwisethe MAC entity may not increment preamble transmission counter by 1. Ina MAC entity, if no Random Access Response is received within the RAResponse window, or if none of received random access responses containsa random access preamble identifier corresponding to the transmittedrandom access preamble, the random access response reception may beconsidered not successful if the preamble is transmitted a maximumnumber of times by the physical layer. If preamble transmissioncounter=preambleTransMax+1 and if the Random Access Preamble istransmitted on an SCell, the UE may consider the Random Access procedureunsuccessfully completed.

In an example embodiment, a PHY layer may indicate to the MAC layer ofpower ramping suspension when preamble transmission is dropped at thePHY layer on a PRACH opportunity of the LAA SCell due to LBT failure.After receiving such indication MAC layer may not increment the preambletransmission counter, thus avoiding power ramping for the next preambletransmission if it is not dropped. In an example, a PHY layer mayindicate to the MAC layer of power ramping suspension when preambletransmission is dropped at the PHY layer due to LBT failure (LBTindicating that the channel is busy). After receiving such indicationMAC layer may not increment the preamble transmission counter, thusavoiding power ramping for the next preamble transmission.

The MAC layer may instruct a physical layer to transmit a preamble on alicense assisted access (LAA) cell. The physical layer may performlisten-before-talk (LBT) for transmission of the preamble at a preambletransmission opportunity. The physical layer may transmit the preambleif the LBT succeeds, otherwise the physical layer may drop transmissionof the preamble. The physical layer may notify the MAC layer, a powerramping suspension indication when the transmission of the preamble isdropped due to a failure of the LBT. When the MAC layer receives a powerramping suspension notification from the physical layer, the MAC layermay not increment the preamble transmission counter, thus avoiding powerramping for the next preamble transmission. Preamble transmissioncounter may be for a number of physical layer transmissions of thepreamble.

In an LAA cell, a UE physical layer may not be able to transmit a RApreamble (RAP) for a long time or any more on an LAA cell when thechannel is busy. In this case, the UE MAC may keep transmitting RAPbecause the preamble transmission counter may not increase and may notreach preambleTransMax for a relatively long period.

The UE physical layer may or may not be able to transmit the dedicatedpreamble in a next PRACH opportunity on the LAA SCell when the physicallayer is instructed by the MAC layer to transmit a preamble. Preambledropping (e.g. due to LBT) case may be a frequent event in an LAA cellin some scenarios. In an LAA cell, it may be quite frequent that the UEmay hold the dedicated preamble allocated by the network for arelatively long time which may not be efficient from resourceutilization point of view. Ongoing RA procedure on a busy/occupied LAAcell may cause a delay in acquisition of uplink synchronization and mayunnecessarily increase UE battery power and processing powerconsumption. In an LAA cell, the UE MAC may keep transmitting (e.g.instructing the PHY to transmit) RAP on the LAA cell even if the LAAcell on which the PDCCH order initiated random access is on-going cannotbe used for a while. There is a need to consider the random accessprocedure unsuccessfully completed when the UE is not able to transmitrandom access preamble on an LAA cell after many attempts.

In an example embodiment, a new counter is introduced. The new countermay be configured to limit a time duration that the preamble is used forthe RA procedure on the cell. In an example embodiment, a preambletransmission opportunity counter may be configured in the UE. Thepreamble transmission opportunity counter may be configured to count thenumber of preamble transmission attempts in a random access procedure onan LAA cell. The preamble transmission opportunity counter may beconfigured to count the number of physical layer LBT attempts in arandom access procedure on an LAA cell. For example, when a wirelessdevice receives from an eNB a PDCCH order initiating a random accessprocedure, the wireless device may start preamble transmissionopportunity counter. The preamble transmission opportunity counter maybe started at 1. The preamble transmission opportunity counter may beincremented at a preamble transmission opportunity when UE MAC layerinstructs the PHY layer to transmit a preamble (regardless of LBT failsor succeeds) on an LAA cell. The preamble transmission opportunitycounter may indicate the number of preamble transmission attempts byphysical layer. A UE may unsuccessfully complete the RA process when theRA preamble transmission opportunity counter expires (e.g. reaches amaximum counter value) when no random access response is received withina random access response window. The preamble transmission opportunitycounter may not be needed for licensed cells, since power rampingsuspension is expected to be a frequent event in licensed cell. Thepreamble transmission counter may be a first counter configured to counta number of physical layer transmissions of the preamble. The firstcounter may be employed for a licensed cell or an LAA cell. The preambletransmission opportunity may be a second counter configured to limit atime duration that the preamble is used for the RA procedure on an LAAcell. Since power suspension notification is not a frequent event on alicensed cell, there is no need to employ the second counter to limit atime duration that the preamble is used for the RA procedure on alicensed cell. This mechanism may simplify the random access process ona licensed cell, and may improve the efficiency of the RA process on anLAA cell.

For a RACH on SCell, if no corresponding random access response isreceived and if preamble transmission counter is smaller thanpreambleTransMax+1 and preamble transmission opportunity counter issmaller than preambleTransMax+1 then the UE may proceed to the selectionof a random access resource and random access preamble transmission(e.g. in the next RACH resource opportunity).

When a random access procedure on an SCell is unsuccessfully completed,the eNB may initiate another RA procedure on another SCell in the sTAGto make the cells in the sTAG uplink synchronized. There may be onerandom access procedure ongoing at any point in time in a MAC entity. Ifthe MAC entity receives a request for a new random access procedurewhile another is already ongoing in the MAC entity, it is up to UEimplementation whether to continue with the ongoing procedure or startwith the new procedure. In an example implementation, a UE may cancelthe ongoing process and start with the new procedure

FIG. 14 is an example signal flow of a random access process in alicensed cell as per an aspect of an embodiment of the presentinvention. A UE may transmit the random access preamble on a RACHresource. If no random access response is received within the RAresponse window, or if none of received random access responses containsa random access preamble identifier corresponding to the transmittedrandom access preamble, the random access response reception isconsidered not successful and the MAC entity may increase preambletransmission counter (PTC) by one if the notification of power rampingsuspension has not been received from lower layers. In FIG. 14, anotification of power ramping suspension is received in the secondpreamble transmission opportunity.

If preamble transmission counter is lower than preambleTransMax+1, theUE may proceed to the selection of a Random Access Resource,determination of preamble power employing the PTC, and the transmissionof the Random Access Preamble. The UE may transmit RAP for a maximum ofpreamble transmission counter (e.g. preambleTransMax) and mayunsuccessfully complete the process when no corresponding RAR isreceived.

The eNB may consider the RA preamble released and RA processunsuccessfully completed if during the RA process no preamble isreceived from the UE. The eNB may start a new RA process on a differentcell or may take a different action. In FIG. 14, the UE may terminate aRA process (e.g. after preambleTransMax transmissions=3). The processmay limit the UE battery power consumption and preamble holding period.

A MAC entity may maintain a preamble transmission counter for a numberof preamble transmissions that has been performed. When this counterreaches a configurable maximum value the UE may consider the randomaccess procedure unsuccessfully completed. The UE may release thepreamble. If the cell is LAA, a UE may drop one or more preambles duringthe random access procedure and may not increase the preambletransmission counter when preamble transmission is dropped. For example,an eNB may configure the UE to send a preamble 8 times the but the UEmay drop six of those 8 preamble transmissions. This may result in thatthe UE employs the preamble 14 times instead of 8. The UE may releasethe preamble after 14 preamble transmission opportunities rather thanthe configured 8 times. The eNB may not be able to determine when thepreamble becomes available again. In an example scenario, the number ofpreamble dropping due to LBT failure on an LAA cell may be excessive.

In an example embodiment, a limit may be implemented for how long the UEcan use a dedicated preamble on an LAA cell. The dedicated preamble maybe used for a limited time regardless of LBT result. This may enableefficiently managing available dedicated RAPs. In order to limit thelife time of a dedicated RAP on LAA SCell, a counter or timer other thanthe preamble transmission counter may be implemented for an LAA SCell.

FIG. 15 and FIG. 16 are example signal flows of random access process inan LAA cell as per an aspect of an embodiment of the present invention.FIG. 15 and FIG. 16 show example RA processes when power rampingsuspension(s) occurs in an LAA cell. FIG. 15 and FIG. 16 show example RAprocesses on an LAA cell in a busy/congested frequency. The UE may dropone or more preamble transmissions and RA process may take a long andun-deterministic period. For example, a UE in a bad coverage quality maynot be able to perform preambleTransMax transmissions of the preambleduring a relatively long period. This process may unnecessarily consumeUE processing and battery power.

In an example embodiment, a new timer may be introduced. In an exampleembodiment, a preamble transmission process timer may be configured inthe UE. For example, a UE may start the timer when it receives a PDDCHorder and starts the RA process. A UE may unsuccessfully complete the RAprocess when the RA process timer expires and the RA process is notsuccessfully completed. The RA process timer may enable that UEterminates/completes the RA process after a limited period of time. Inan example embodiment, the maximum preamble transmission process timerand its value may be configured by an RRC message transmitted by an eNBand received by the UE. In an example embodiment, the maximum preambletransmission process timer may have a fixed value which ispre-configured in the UE and eNB.

In an example embodiment, a new counter may be introduced. In an exampleembodiment, a preamble transmission opportunity counter may beconfigured in the UE. For example, a UE may start the preambletransmission opportunity counter at 1 when it receives a PDDCH order tostart the RA process. The preamble transmission opportunity counter maybe started at one. The preamble transmission opportunity counter mayincremented when/if the UE MAC entity attempts a preamble transmissionby instructing a UE physical layer to transmit the preamble in a randomaccess channel opportunity. A UE may unsuccessfully complete the RAprocess when the RA preamble transmission opportunity counter expires(e.g. reaches a certain value) and no random access response is receivedwithin a random access response window. The preamble transmissionopportunity counter may enable that the UE terminates/completes the RAprocess after a limited number of random access transmission attempts.The new counter may be called by other names, such as, a preambletransmission attempt counter, RA process counter, and/or the like. Thenew counter is configured to limit a time duration that the preamble isused for the RA procedure on the cell. The MAC entity may maintain apreamble transmission opportunity counter and a preamble transmissioncounter in a random access procedure.

In an example embodiment, a maximum number of preamble transmissions maybe configured by an RRC message transmitted by an eNB and received bythe UE. In an example embodiment, the maximum number of preambletransmissions may have a fixed value which is pre-configured in the UEand eNB. The maximum number of preamble transmissions may be configuredin terms of RACH transmission opportunities. In an example, maximumnumber of preamble transmissions may be selected and configured from alimited number of values (3, 10, 20 RACH transmission opportunities). Inan example, maximum number of preamble transmissions may be selected andconfigured from a limited number of values (3, 10, 20 RACHtransmission). In example FIG. 14, maximum number of preambletransmissions may be configured as 4. In example FIG. 15, maximum numberof preamble transmissions may be configured as 5. In example FIG. 16,maximum number of preamble transmission may be configured as 8.

For example, in FIG. 15, a random access procedure is initiated when aneNB transmits a PDCCH order to a UE for transmission of a preamble on anLAA cell. The UE may start the preamble transmission counter (set thepreamble transmission counter to 1). The UE may start the preambletransmission opportunity counter (set the preamble transmissionopportunity counter to 1). When a preamble is transmitted and if thenotification of power ramping suspension has not been received fromlower layers (e.g. due to LBT at the PHY layer), the MAC entity mayincrement preamble transmission counter by 1. If there has been apreamble transmission attempt by the MAC layer (regardless of LBT beingsuccessful or not) the MAC entity may increment preamble transmissionopportunity counter by 1. In FIG. 15, the random access procedure isconsidered unsuccessfully completed after five preamble transmissionprocess attempts. The maximum number of preamble transmissions isconfigured as five. The physical layer transmits the preamble fourtimes, and the physical layer was not able to transmit the preamble in atransmission opportunity once due to LBT.

For example, in FIG. 16, a random access procedure is initiated when aneNB transmits a PDCCH order to a UE for transmission of a preamble on anLAA cell. The UE may start the preamble transmission counter (set thepreamble transmission counter to 1). The UE may start the preambletransmission opportunity counter (set the preamble transmissionopportunity counter to 1). When a preamble is transmitted and if thenotification of power ramping suspension has not been received fromlower layers (e.g. due to LBT at the PHY layer), the MAC entity mayincrement preamble transmission counter by 1. If there has been apreamble transmission attempt by the MAC layer (regardless of LBT beingsuccessful or not) the MAC entity may increment preamble transmissionopportunity counter by 1. In FIG. 16, the random access procedure isconsidered unsuccessfully completed after eight preamble transmissionprocess attempts. The maximum number of preamble transmissions isconfigured as eight. The physical layer transmitted the preamble once,and the physical layer was not able to transmit the preamble in atransmission opportunity seven times due to LBT.

In a MAC entity and for RA process on an LAA cell, if no Random AccessResponse is received within the RA Response window, or if none ofreceived Random Access Responses contains a Random Access Preambleidentifier corresponding to the transmitted Random Access Preamble, theRandom Access Response reception may be considered unsuccessfullycompleted. In a MAC entity if the notification of power rampingsuspension has not been received from lower layers (e.g. PHY layer), theMAC entity may increment preamble transmission counter by 1, otherwisethe MAC entity may not increment preamble transmission counter by 1. Ifpreamble transmission counter=preambleTransMax+1 and if the RandomAccess Preamble is transmitted on an SCell, the UE may consider theRandom Access procedure unsuccessfully completed. For a RA process on anLAA cell, the MAC entity may increment preamble transmission opportunitycounter by 1 when the MAC entity attempts transmission of the preambleon the LAA cell. If preamble transmission opportunity counter increasesa maximum number of preamble transmissions (e.g. equal to maximumPTOC+1), the UE may consider the Random Access procedure unsuccessfullycompleted. For a RACH on SCell, if preamble transmission counter issmaller than maximum number of preamble transmissions and preambletransmission opportunity counter is smaller than maximum number ofpreamble transmissions then the ue may proceed to the selection of arandom access resource and random access preamble transmission (e.g. inthe next RACH resource opportunity). It is clear based on the abovedescription that preamble transmission counter is always less than orequal to the preamble transmission opportunity counter.

In an example embodiment, when the RA preamble transmission opportunitycounter expires (exceeds a preconfigured value) and UE does not receivea RAR corresponding to the RAP, the UE considers that the RA process isunsuccessfully completed. In an example, a counter may be used by theeNB. If the eNB does not receive a RAP before the counter expires, theeNB may determine that the RA process is unsuccessfully completed. In anexample embodiment, maximum RA preamble transmission opportunity countermay be implemented for LAA cell(s).

In an example embodiment, a maximum RA preamble transmission IE may beemployed for configuration of one or more RACHs. In an exampleembodiment, a maximum RA preamble transmission IE may be configured as aparameter for RA processes employing cells in LAA and/or licensed cells.The preambleTransMax IE may be employed for configuring maximum preambletransmission number for preamble transmission opportunity counter. Thisprocess may reduce flexibility in configuring different maximum countervalues for a RACH process, and the same value may be used for maximumpreamble transmission counter and maximum preamble transmissionopportunity counter. This may reduce signaling overhead. With thisconfiguration, a UE may not need to store and/or maintain multiplemaximum RA preamble transmission IE values for a cell, and the samemaximum value may apply to different RA counters. A maximum countervalue may be stored for a random access process regardless of whetherthe cell is licensed or unlicensed.

In an example embodiment, different cells may have different maximumcounter values. At least one RRC message may comprise a first distinctmaximum preamble transmission information element for RACH of a firstcell and a second distinct maximum preamble transmission informationelement for a second cell. This process may allow flexibility inconfiguring maximum preamble transmission values for the first cell andthe second cell. This may increase the signaling overhead, and providesa needed flexibility in configuring RA process on different cells. In anexample embodiment, at least one RRC message may comprise differentmaximum values for preamble transmission counter and preambletransmission opportunity counter.

FIG. 17 is an example signal flow of a random access process in an LAAcell as per an aspect of an embodiment of the present invention. FIG. 17shows an example, in which the UE receives a RAR corresponding thetransmitted RAP before preamble transmission counter or RA preambletransmission opportunity counter reach a maximum preamble transmissionvalue (expires). In such a scenario, the UE may consider that the RAprocess is successfully completed.

FIG. 18 is an example signal flow of a random access process in an LAAcell as per an aspect of an embodiment of the present invention. FIG. 18shows an example, wherein UE receives a new PDCCH order before the RApreamble transmission opportunity counter expires (e.g. reaches amaximum value) in an ongoing RACH process. The MAC entity in the UE mayrestart (at 1) the RA preamble transmission opportunity counter andpreamble transmission counter when it receives a PDCCH order. The UE maystart the new RA process according to the PDCCH order and cancel theongoing RA process.

The maximum RA preamble transmission opportunity counter may beconfigured in terms of RACH transmission opportunities (when MAC layerinstructs the physical layer and attempts a preamble transmission). Forexample, maximum RA preamble transmission may be selected and configuredfrom a limited number of values (1, 2, 3, 10, 20 RACH transmissionattempts/opportunities). In an example embodiment, a maximum RA preambletransmission may be configured as infinity. This may practically meanthat this counter would never expire.

Example embodiments may provide a mechanism for considering a RA processunsuccessfully completed in a UE and/or eNB. This mechanism may preventor reduce the possibility wherein a UE may stay in a RACH process for along period and try to transmit a preamble for a long period on abusy/congested frequency. The mechanism may reduce battery and processpower consumption in a UE and or an eNB by allowing unsuccessfulcompletion of a RA process.

FIG. 19 is an example flow diagram as per an aspect of an embodiment ofthe present invention. The random access procedure may comprise some ofthe main steps described here and not all the detailed actions taken bythe UE are shown in the flow diagram in FIG. 19. The random accessprocedure may be initiated by a PDCCH order, by the MAC sublayer itselfor by the RRC sublayer. Random Access procedure on an SCell may beinitiated by a PDCCH order as shown in block 1900. If a MAC entityreceives a PDCCH transmission consistent with a PDCCH order masked withits C-RNTI, and for a specific serving cell, the MAC entity may initiatea random access procedure on this serving cell. For random access on theSpCell a PDCCH order or RRC optionally indicate the ra-PreambleIndex andthe ra-PRACH-MaskIndex; and for Random Access on an SCell, the PDCCHorder may indicates the ra-PreambleIndex with a value different from000000 and the ra-PRACH-MaskIndex. For the pTAG preamble transmission onPRACH and reception of a PDCCH order are only supported for SpCell.

Before the procedure can be initiated, at least some of the followinginformation for related Serving Cell may be to be available: theavailable set of PRACH resources for the transmission of the RandomAccess Preamble, prach-ConfigIndex; the groups of Random AccessPreambles and the set of available Random Access Preambles in a group(e.g for SpCell): The preambles that are contained in Random AccessPreambles group A and Random Access Preambles group B are calculatedfrom the parameters numberOfRA-Preambles and sizeOfRA-PreamblesGroupA:If sizeOfRA-PreamblesGroupA is equal to numberOfRA-Preambles then thereis no Random Access Preambles group B. The preambles in Random AccessPreamble group A are the preambles 0 to sizeOfRA-PreamblesGroupA−1 and,if it exists, the preambles in Random Access Preamble group B are thepreambles sizeOfRA-PreamblesGroupA to numberOfRA-Preambles−1 from theset of 64 preambles as defined in. if Random Access Preambles group Bexists, the thresholds, messagePowerOffsetGroupB and messageSizeGroupA,the configured UE transmitted power of the Serving Cell performing theRandom Access Procedure, PCMAX, c, and the offset between the preambleand Msg3, deltaPreambleMsg3, that are required for selecting one of thetwo groups of Random Access Preambles (e.g for SpCell). The RA responsewindow size ra-ResponseWindowSize. the power-ramping factorpowerRampingStep. the maximum number of preamble transmissionpreambleTransMax. the initial preamble powerpreambleInitialReceivedTargetPower. the preamble format based offsetDELTA_PREAMBLE. the maximum number of Msg3 HARQ transmissionsmaxHARQ-Msg3Tx (SpCell only). the Contention Resolution Timermac-ContentionResolutionTimer (SpCell only). The above parameters may beupdated from upper layers before a Random Access procedure is initiated.Other information/parameters may be available as well.

In an example embodiment, the random access procedure may be performedas follows: The UE may flush the Msg3 buffer; set the preambletransmission counter to 1 and set the preamble transmission opportunitycounter to 1 (as shown in block 1905); set the backoff parameter valueto 0 ms; for the RN, suspend any RN subframe configuration; and proceedto the selection of the Random Access Resource (as shown in block 1910).There may be one Random Access procedure ongoing at any point in time ina MAC entity. In an example, if the MAC entity receives a request for anew random access procedure while another is already ongoing in the MACentity, the UE may start with the new procedure and cancel the ongoingprocess.

In an example embodiment, the random access resource selection proceduremay be performed as follows: if ra-preambleindex (random accesspreamble) and ra-PRACH-MaskIndex (PRACH Mask Index) have been explicitlysignalled and ra-PreambleIndex is not 000000: the Random Access Preambleand the PRACH Mask Index are those explicitly signalled, else the RandomAccess Preamble may be selected by the MAC entity as follows: If Msg3has not yet been transmitted, the MAC entity may: if Random AccessPreambles group B exists and if the potential message size (UL dataavailable for transmission plus MAC header and, where required, MACcontrol elements) is greater than messageSizeGroupA and if the pathlossis less than PCMAX,c (of the Serving Cell performing the Random AccessProcedure)−preambleInitialReceivedTargetPower−deltaPreambleMsg3−messagePowerOffsetGroupB,then: select the Random Access Preambles group B; else: select theRandom Access Preambles group A, Else, if Msg3 is being retransmitted,the MAC entity may: select the same group of Random Access Preambles aswas used for the preamble transmission attempt corresponding to thefirst transmission of Msg3, randomly select a Random Access Preamblewithin the selected group; The random function may be such that each ofthe allowed selections can be chosen with equal probability; and/or setPRACH Mask Index to 0.

In an example embodiment, the UE may determine the next availablesubframe containing PRACH permitted by the restrictions given by theprach-ConfigIndex, the PRACH mask index and physical layer timingrequirements (a MAC entity may take into account the possible occurrenceof measurement gaps when determining the next available PRACH subframe);if the transmission mode is TDD and the PRACH mask index is equal tozero: if ra-PreambleIndex was explicitly signalled and it was not 000000(e.g., not selected by MAC): randomly select, with equal probability,one PRACH from the PRACHs available in the determined subframe, Else:randomly select, with equal probability, one PRACH from the PRACHsavailable in the determined subframe and the next two consecutivesubframes, else: determine a PRACH within the determined subframe inaccordance with the requirements of the PRACH Mask Index. The UE mayproceed to the transmission of the random access preamble.

In an example embodiment, random Access preamble transmission may beperformed as follows: The MAC entity may setPREAMBLE_RECEIVED_TARGET_POWER topreambleInitialReceivedTargetPower+DELTA_PREAMBLE+(PREAMBLE_TRANSMISSION_COUNTER−1)*powerRampingStep;and instruct the physical layer to transmit a preamble using theselected PRACH, corresponding RA-RNTI, preamble index andPREAMBLE_RECEIVED_TARGET_POWER (as shown in block 1915).

In an example embodiment, once the Random Access Preamble is transmittedand regardless of the possible occurrence of a measurement gap, the MACentity may monitor the PDCCH of the SpCell for Random Access Response(s)identified by the RA-RNTI defined below (as shown in block 1920), in theRA Response window which, e.g, starts at the subframe that contains theend of the preamble transmission plus three subframes and has lengthra-ResponseWindowSize subframes. In an example, the RA-RNTI associatedwith the PRACH in which the Random Access Preamble is transmitted, iscomputed as: RA-RNTI=1+t_id+10*f_id, where t_id is the index of thefirst subframe of the specified PRACH (0≤t_id<10), and t_id is the indexof the specified PRACH within that subframe, in ascending order offrequency domain (0≤f_id<6). The MAC entity may stop monitoring forrandom access response(s) after successful reception of a random accessresponse containing random access preamble identifiers that matches thetransmitted random access preamble (as shown in block 1925).

In an example embodiment, if a downlink assignment for this TTI has beenreceived on the PDCCH for the RA-RNTI and the received TB issuccessfully decoded, the MAC entity may regardless of the possibleoccurrence of a measurement gap: if the Random Access Response containsa Backoff Indicator subheader: set the backoff parameter value asindicated by the BI field of the Backoff Indicator subheader. Else, setthe backoff parameter value to 0 ms.

If the Random Access Response contains a Random Access Preambleidentifier corresponding to the transmitted Random Access Preamble (inblock 1925), the MAC entity may: consider this Random Access Responsereception successful and apply the following actions for the servingcell where the Random Access Preamble was transmitted. Ifra-PreambleIndex was explicitly signalled and it was not 000000 (e.g.,not selected by MAC): consider the Random Access procedure successfullycompleted.

If no Random Access Response is received within the RA response window,or if none of received Random Access Responses contains a Random AccessPreamble identifier corresponding to the transmitted Random AccessPreamble, the Random Access Response reception is considered notsuccessful and the MAC entity may: if the notification of power rampingsuspension has not been received from lower layers: increment preambletransmission counter by 1 (as shown in block 1930); if preambletransmission counter=preambleTransMax+1 (as shown in block 1935): if theRandom Access Preamble is transmitted on the SpCell: indicate a RandomAccess problem to upper layers; if the Random Access Preamble istransmitted on an SCell: consider the Random Access procedureunsuccessfully completed (as shown in block 1940).

In an example embodiment, if the random access preamble was transmittedon a serving cell operating according to LAA frame structure (LAA cellas shown in block 1960): The UE may increment preamble transmissionattempt counter by 1 (as shown in block 1945); if preamble transmissionattempt counter=preambleTransMax+1 (as shown in block 1950): considerthe Random Access procedure unsuccessfully completed (as shown in block1955). The UE may proceed to the selection of a random access resourceas shown in block 1910.

In an example, blocks 1960, 1945, 1950 and 1955 may be performed beforeblocks 1930, 1935 and 1940. In an example embodiment, blocks 1960, 1945,1950 and 1955 and 1930, 1935 and 1940 may be combined together. In anLAA cell, PTOC is greater or equal than PTC. When PTOC is greater thanmax counter, PTC is also greater than the max counter. When the value ofPTOC is smaller than the max counter, PTC is also smaller than the maxcounter. In an example, for an LAA cell, the blocks 1935 and 1950 may becombined as PTC or PTOC greater than max counter to reduce the number ofblocks. Other variations of the flow chart may be implemented to achievethe same results. Some blocks may be combined and/or some blocks couldbe broken down into sub-blocks.

In an example embodiment, at the completion of the random accessprocedure, the MAC entity may: discard explicitly signalledra-PreambleIndex and ra-PRACH-MaskIndex, if any; flush the HARQ bufferused for transmission of the MAC PDU in the Msg3 buffer. In addition,the RN may resume the suspended RN subframe configuration, if any.

The MAC entity may have a configurable timer timeAlignmentTimer per TAG.The timeAlignmentTimer is used to control how long the MAC entityconsiders the Serving Cells belonging to the associated TAG to be uplinktime aligned. The MAC entity may: when a timing advance command MACcontrol element is received: apply the timing advance command for theindicated TAG; start or restart the timeAlignmentTimer associated withthe indicated TAG.

In an example embodiment, when a timing advance command is received in arandom access response message for a serving cell belonging to a TAG: ifthe random access preamble was not selected by the MAC entity: apply thetiming advance command for this TAG; start or restart thetimeAlignmentTimer associated with this TAG, else, if thetimeAlignmentTimer associated with this TAG is not running: apply thetiming advance command for this TAG; start the timeAlignmentTimerassociated with this TAG; when the contention resolution is considerednot successful, stop timeAlignmentTimer associated with this TAG.

In an example embodiment, when a timeAlignmentTimer expires: if thetimeAlignmentTimer is associated with the pTAG: flush HARQ buffers forserving cells; notify RRC to release PUCCH/SRS for serving cells; clearany configured downlink assignments and uplink grants; consider runningtimeAlignmentTimers as expired; else if the timeAlignmentTimer isassociated with an sTAG, then for serving cells belonging to this TAG:flush all HARQ buffers; notify RRC to release SRS.

When the MAC entity stops uplink transmissions for an SCell due to thefact that the maximum uplink transmission timing difference or themaximum uplink transmission timing difference the MAC entity can handlebetween TAGs of this MAC entity is exceeded, the MAC entity considersthe timeAlignmentTimer associated with the SCell as expired. The MACentity may not perform any uplink transmission on a serving cell exceptthe random access preamble transmission when the timeAlignmentTimerassociated with the TAG to which this serving cell belongs is notrunning. When the timeAlignmentTimer associated with the pTAG is notrunning, the MAC entity may not perform any uplink transmission on anyserving cell except the Random Access Preamble transmission on theSpCell. The MAC entity may not perform any sidelink transmission whichis performed based on UL timing of the corresponding serving cell andany associated SCI transmissions when the correspondingtimeAlignmentTimer is not running A MAC entity stores or maintains NTAupon expiry of associated timeAlignmentTimer. The MAC entity applies areceived timing advance command MAC control element and startsassociated timeAlignmentTimer also when the timeAlignmentTimer is notrunning.

FIG. 20 is an example flow diagram as per an aspect of an embodiment ofthe present invention. A wireless device may receive a control (e.g.PDCCH) order to transmit a preamble as a part of a random access (RA)procedure on a cell at 2110. According to an embodiment, the controlorder may comprise a physical downlink control channel (PDCCH) ordercomprising a preamble index and a random access mask index.

At 2020, the wireless device may instruct, a physical layer by a MAClayer, to transmit the preamble on the cell. At 2030, a determinationmay be made as to whether a corresponding Random Access Response (RAR)is received in response to a preamble transmission. According to anembodiment, the wireless device may further monitor a downlink channelfor the corresponding random access response within a random accessresponse window. The corresponding random access response may comprise apreamble identifier that matches the preamble. If the determination at2030 is positive, a RAR process may be performed at 2040. According toan embodiment, when the wireless device receives the correspondingrandom access response, the random access procedure may be consideredsuccessfully completed.

A determination may be made as to whether the RA procedure wassuccessfully completed if the determination at 2030 is negative. Forexample, the RA procedure may be considered to be unsuccessfullycompleted (2080) if a first condition based on a first counter is met(determined at 2050) regardless of whether the cell is licensed orlicensed-assisted-access (LAA). The first counter may be configured tocount a number of physical layer transmissions of the preamble.Otherwise, the RA procedure may be considered to be unsuccessfullycompleted (2080) if a second condition based on a second counter is met(determined at 2070) and the cell is LAA (determined at 2060). Thesecond counter may be employed only if the cell is LAA. The secondcounter may be configured to limit a time duration that the preamble isused for the RA procedure on the cell.

Not all the detailed mechanisms are shown in the flow diagrams ofexample embodiments. Other variations of the mechanism may beimplemented. For example, when the physical layer does not transmit thepreamble and indicate a power ramping suspension, the MAC/PHY layer maynot monitor a downlink channel for a corresponding RAR, since thepreamble was not transmitted. In an example, first counter and secondcounter may be processed together, instead of being processedseparately. This may reduce the number of tasks, and may result in thesame outcome. In an example, the second counter may not be configured orstarted when the cell is a licensed cell.

According to an embodiment, the wireless device may further set apreamble power parameter employing the first counter. According to anembodiment, the wireless device may further, in response to receivingthe control order: start the first counter, and start the secondcounter.

According to an embodiment, when the cell is LAA, the wireless devicemay perform, by the physical layer, listen-before-talk (LBT) fortransmission of the preamble at a transmission opportunity. If the LBTsucceeds, the preamble may be transmitted by the physical layer.Otherwise, transmission of the preamble may be dropped. When thetransmission of the preamble is dropped due to a failure of the LBT, apower ramping suspension indication from the physical layer may bereceived by the MAC layer. According to an embodiment, the wirelessdevice may further comprise: increasing the first counter when thepreamble is transmitted by the physical layer; and/or increasing thesecond counter when the physical layer performs LBT for transmission ofthe preamble at a transmission opportunity of the preamble.

According to an embodiment, the second counter may be configured tocount a number of transmission opportunities/attempts of the preamble inan LAA cell. According to an embodiment, the wireless device may furtherselect random access resources for preamble transmission if, forexample: the corresponding random access response is not received; thefirst condition is not met; and/or the second condition is not met.

According to an embodiment, the wireless device may further consider thefirst condition met when the first counter reaches a maximum countervalue. According to an embodiment, the wireless device may furtherreceive a radio resource control (RRC) message indicating the maximumcounter value. According to an embodiment, the wireless device mayfurther consider the second condition met when the second counterreaches the maximum counter value. According to an embodiment, thewireless device may further receive an RRC message indicating themaximum counter value. According to an embodiment, the wireless devicemay further comprise receiving at least one RRC message comprising, forexample: configuration parameters of a plurality of cells comprising thecell; random access resource information elements of a random accesschannel (RACH) on the cell; a random access response window informationelement; and/or a maximum RA transmission counter information element.

FIG. 21 is an example flow diagram as per an aspect of an embodiment ofthe present invention. A wireless device may instruct, a physical layerby a MAC layer, to transmit a preamble as a part of a random access (RA)procedure on a licensed assisted access (LAA) cell at 2110. At 2120, anLBT for transmission of the preamble may be performed at a transmissionopportunity of the preamble.

At 2130, a determination may be made as to whether a correspondingRandom Access Response (RAR) is received in response to a preambletransmission. If the determination at 2130 is positive, a RAR processmay be performed at 2140. According to an embodiment, when the wirelessdevice receives the corresponding random access response, the randomaccess procedure may be considered successfully completed.

A determination may be made as to whether the LBT was successfullycompleted at 2150 if the determination at 2130 is negative. A firstcounter may be increased (2160) when the LBT is successful. A secondcounter may be increased (2170) regardless of the success or failure ofthe LBT. The RA procedure may be considered unsuccessfully completed(2195) if a first condition based on the first counter is met at 2180.Otherwise RA procedure may be considered unsuccessfully completed (2195)if a second condition based on the second counter is met at 2190.

According to an embodiment, the wireless device may further perform, bythe physical layer, listen-before-talk (LBT) for transmission of thepreamble at a transmission opportunity. According to an embodiment, thewireless device may further transmit, by the physical layer, thepreamble if the LBT succeeds, otherwise drop transmission of thepreamble. According to an embodiment, the wireless device may furtherconsider the random access procedure successfully completed when thewireless device receives the corresponding random access response.According to an embodiment, the wireless device may further receive acontrol (e.g. PDCCH) order configured to initiate the random accessprocedure on the LAA cell, start the first counter in response toreceiving the control order, and start the second counter in response toreceiving the control order.

A wireless device may comprise one or more processors and memory storinginstructions that, when executed, cause the wireless device to performas series of actions. For example, the instructions may cause theprocessor to instruct, a physical layer by a MAC layer, to transmit apreamble as a part of a random access (RA) procedure on a licensedassisted access (LAA) cell. The instructions may cause the processor toperform an LBT for transmission of the preamble at a transmissionopportunity of the preamble. When a corresponding random access responseis not received, the instructions may cause the processor to: increase afirst counter when the LBT is successful, increase a second counterregardless of success or failure of the LBT; and consider the RAprocedure unsuccessfully completed if a first condition based on thefirst counter is met, otherwise consider the RA procedure unsuccessfullycompleted if second a condition based on the second counter is met.

FIG. 22 is an example flow diagram as per an aspect of an embodiment ofthe present invention. At 2210, a wireless device may receive a controlorder initiating a random access procedure on a first cell during anongoing random access procedure on a second cell. According to anembodiment, the control order may be a physical downlink control channel(PDCCH) comprising a preamble index and a random access mask index.According to an embodiment, the first cell may be the same as the secondcell. According to an embodiment, the first cell may be different thanthe second cell.

At 2215, a first counter and a second counter may be restarted. At 2220,the wireless device may instruct, a physical layer by a MAC layer, totransmit the preamble on the first cell. At 2230, a determination may bemade as to whether a corresponding Random Access Response (RAR) isreceived in response to a preamble transmission. If the determination at2230 is positive, a RAR process may be performed at 2240. According toan embodiment, the wireless device may further monitor a downlinkchannel for the corresponding random access response within a randomaccess response window. The corresponding random access response maycomprise a preamble identifier that matches the preamble.

A determination may be made as to whether the RA procedure wassuccessfully completed at 2250 if the determination at 2230 is negative.The RA procedure may be considered unsuccessfully completed (2280) if afirst condition based on the first counter is met at 2250, regardless ofwhether the first cell is licensed or licensed-assisted-access (LAA).The first counter may be configured to count a number of physical layertransmissions of the preamble. Otherwise, the RA procedure may beconsidered unsuccessfully completed (2280) if a second condition basedon the second counter is met at 2270 and the first cell is LAA(determined at 2260). The second counter may be employed only if thefirst cell is LAA. The second counter may be configured to limit a timeduration that the preamble is used for the RA procedure on an LAA cell.

According to an embodiment, when the first cell is LAA, the wirelessdevice may further perform, by the physical layer, listen-before-talk(LBT) for transmission of the preamble at a transmission opportunity.The preamble may be transmitted by the physical layer if the LBTsucceeds. Otherwise, transmission of the preamble may be dropped. Thewireless device may receive, by the MAC layer, a power rampingsuspension indication from the physical layer when the transmission ofthe preamble is dropped due to a failure of the LBT.

According to an embodiment, the wireless device may further cancel theongoing random access procedure. According to an embodiment, thewireless device may further consider the random access proceduresuccessfully completed when the wireless device receives thecorresponding random access response.

According to an embodiment, the wireless device may further set apreamble power parameter employing the first counter. According to anembodiment, the second counter may be configured to count a number oftransmission opportunities/attempts of the preamble. According to anembodiment, the wireless device may further consider the first conditionmet when the first counter reaches a maximum counter value. According toan embodiment, the wireless device may further receive a radio resourcecontrol (RRC) message indicating the maximum counter value. According toan embodiment, the wireless device may further consider the secondcondition met when the second counter reaches the maximum counter value.The According to an embodiment, the wireless device may further receivean RRC message indicating the maximum counter value. The first countermay be increased when the preamble is transmitted by the physical layer.The second counter may be increased when the physical layer performs LBTfor transmission of the preamble at a transmission opportunity of thepreamble on an LAA cell.

According to an embodiment, the wireless device may further selectrandom access resources for preamble transmission if, for example: thecorresponding random access response is not received, the firstcondition is not met, and/or the second condition is not met.

According to an embodiment, the wireless device may further receive atleast one RRC message. RRC message(s) may comprise configurationparameters of a plurality of cells comprising the first cell and thesecond cell. RRC message(s) may comprise random access resourceinformation elements of a random access channel (RACH) on the first celland the second cell. RRC message(s) may comprise a random accessresponse window information element. RRC message(s) may comprise amaximum RA transmission counter information element.

FIG. 23 is an example flow diagram as per an aspect of an embodiment ofthe present invention. At 2310, a wireless device may receive a controlorder initiating a random access procedure on a first licensed assistedaccess (LAA) cell during an ongoing random access procedure on a secondLAA cell. At 2315, a first counter and a second counter may berestarted. At 2320, the wireless device may instruct, a physical layerby a MAC layer, to transmit a preamble as a part of a random access (RA)procedure on the first LAA cell. At 2325, an LBT for transmission of thepreamble may be performed at a transmission opportunity of the preamble.

At 2330, a determination may be made as to whether a correspondingRandom Access Response (RAR) is received in response to a preambletransmission. In an example, if the preamble is not transmitted (e.g.because of LBT failure or power issues) by the physical layer, then thewireless device may not monitor for RAR and may not receive a RAR. Ifthe determination at 2330 is positive, a RAR process may be performed at2340.

A determination may be made as to whether the LBT was successful 2350 ifthe determination at 2330 is negative. The first counter may beincreased at 2370 when the LBT is successful (determined at 2350). Thesecond counter may be increased at 2360 regardless of success or failureof the LBT.

The RA procedure may be considered unsuccessfully completed at 2395 if afirst condition based on the first counter is met at 2380. Otherwise,the RA procedure may be considered unsuccessfully completed at 2395 if asecond condition based on the second counter is met at 2390. Accordingto an embodiment, the wireless device may consider the random accessprocedure successfully completed when the wireless device receives thecorresponding random access response.

According to an embodiment, the wireless device may comprise one or moreprocessors and memory storing instructions that, when executed, causethe wireless device to perform a series of actions as described herein.

A TA (timing advance) value may be used by a UE to achieve uplink timealignment so that the received uplink signals are time aligned at theeNB. A TA value indicates to the UE how much it may advance thetransmission of the uplink subframe in relation to the reception of thedownlink subframe. The UE may, for a random access procedure, assume aTA value of zero. The transmission of the preamble may be advanced intime by zero in relation to the reception of the downlink subframestart, e.g. the preamble may be transmitted upon reception of the startof the downlink subframe.

The eNB may, upon reception of the preamble, calculate the difference inneeded uplink reception timing and the actual reception timing of thepreamble. This difference may be indicated in the timing advance command(TAC) which is sent to the UE in a random access response message. Whenthe UE has applied the received TAC, the subsequent uplink transmissionsmay be advanced accordingly. Uplink transmissions may arrive timealigned at the eNB. During the random access procedure the eNB mayprovide the UE with an initial TA value. This “initial TA value” may inmany small cell scenarios be zero.

When multiple TAGs are supported, TAGs including SCell(s) may beconfigured in addition to the PCell TAG. A random access process may beperformed on an SCell of an sTAG. An eNB may transmit a TAC in a RAR tostart the TAT of the sTAG and achieve uplink time alignment for servingcells belonging to the sTAG.

Carrier aggregation scenarios containing small cells offered by e.g.femto cells, RRHs and LAA cells may be supported. In some realizationsof these scenarios a cell radius of a low power node may be small (e.g.smaller than or around 78 meters, or smaller than around 100 m). Somecovered UEs may have a TA value equal to zero.

One TA value-step is 16*Ts which equals around 0.52 μs or about 156meters propagation distance. The TA value may compensate for the roundtrip time. In an example embodiment, UEs which are within 78 meters froma node may use a TA value of zero for uplink transmissions to that node.The UE may assume an initial TA value of zero, when a TAG is created.Given that UEs assume an initial TA value of zero also for a newlycreated TAG the eNB may, instead of ordering a random access procedure,just send a TAC MAC CE with TA value of zero to these UEs. These UEs maynot need to perform random access on those SCells to achieve uplinksynchronization.

TACs may also be received in a TAC MAC CE. The UE may assume an initialTA value of zero. The eNB may have the possibility to trigger start of aUE TAT with a TAC MAC CE containing zero. The UE may start theassociated TAT without the need to perform a random access procedure.RACH load, latency and the possibility of random access failure may bereduced. When a random access procedure is not performed, it may bepossible to reduce the number of serving cells which needs to beconfigured with RACH resources. In an example embodiment, RACH resourcesmay not be configured for any serving cell in an sTAG and a UE mayemploy TAC MAC CE to adjust UE uplink transmission timings.

It may be up to the eNB to determine whether a UE may use a randomaccess process or not. A TAC MAC CE may start the TAT and uplinksynchronize the TAG. Upon configuration of a new TAG, the UE mayinitiate the associated TA value to zero. To obtain initial UL timealignment for an sTAG, an eNB may initiate a random access procedure ormay transmit a TAC MAC CE.

A UE may save the TA value upon expiry of associated TAT. A received TACMAC CE may be applied by the UE when the associated TAT is not running.The eNB may send a TAC MAC CE (e.g. with value zero) to start the TATand avoid an unnecessary random access procedure. An eNB may performthis when the eNB wants to get a UE UL synchronized in a certain TAGafter expiry of the corresponding TAT. This mechanism may reduce RACHload, uplink transmission delay and possibility of RA failure.

In an example embodiment, a UE may be able to reuse a stored TA valueeven though the associated TAT has expired. For example, a UE movingwith a speed of 6 km/h and a TAT value of 20.48 seconds may move lessthan 36 meters from that the UE has started/restarted the TAT before itexpires. A TA value has the span of around 78 meters which means thatthe TA value maintained by the UE is most probably valid for a long timeafter TAT expiry. The eNB may, if it determines suitable, restart such aTAT by a TAC MAC CE instead of ordering a random access procedure.

An eNB may transmit an RRC reconfiguration message to configure a TAG.The eNB may receive an RRC reconfiguration complete message confirmingthat RRC reconfiguration message is received. The eNB may send a MACactivation command to activate an SCell in the TAG. The eNB may send aTAC MAC CE starting the TAT associated with the new TAG to start thecorresponding TAT. This process may introduce unnecessary delays. Thetransmission of the TAC MAC CE may be an unnecessary overhead. In anexample embodiment, when a TAG is created, the initial TA value of zeromay be suitable and it may be unnecessary for the eNB to transmit a TACMAC CE to the UE or to initiate a RA process to start the associatedTAT.

When the TAT of an sTAG is expired, transmission of a MAC CE (e.g. withTA value of zero) or initiation of a RA process may be an unnecessaryoverhead to start the TA timer. The UE may be able to start uplinktransmission with the stored TA whenever it is needed. Existingmechanisms may introduce an unnecessarily slow and suboptimal TAhandling mechanism and may introduce unnecessary additional overhead.There is a need to further improve the existing uplink time alignmentprocess. Some example embodiments of the invention introduce improvedmechanisms for uplink time alignment.

In an example embodiment, an eNB may configure the TAT IE to have afirst value of infinity (or equally as disabled). The eNB may transmitan RRC message comprising a TAT IE for a TAG indicating the first value.When an eNB configures the TAT IE of a TAG as the first value (infinityor disabled), the eNB may indicate that the TAG is uplink synchronizedas long as the TAG is configured. In such a scenario, the eNB may notneed to start a RA process or transmit a MAC TA CE to start the TAT ofthe TAG. This is equivalent to a situation wherein the TAT of the sTAGis always running when sTAG is configured and does not expire. Equally,this may imply that the TAT is disabled, and the UE does not considerprocesses corresponding to a TAT for this TAG.

In this scenario, a UE may start SRS, PUCCH, and/or data transmission onthe SCell of the TAG as soon as the SCell is activated. The UE may applythe TA value of zero for the initial transmission. The eNB may, uponreception of the uplink signals, calculate the difference in neededuplink reception timing and the actual reception timing of the uplinksignals. This difference may be indicated in the Timing Advance Command(TAC) which is sent to the UE. If the network considers the TA value ofzero is not accurate enough, the eNB may adjust the TA via a TA commandafter the first uplink transmission. The UE stores the last updatedvalue of the TA and may use it for the next transmission. For example,when an SCell is deactivated and then activated after a while, the UEmay use the stored value of the TA for uplink transmission when theSCell is activated. When a UE received a MAC TA CE, the UE may apply aTA in the received MAC CE to the stored TA value.

The example embodiment may not require any additional signalingmechanism by RRC messages. Existing related RRC signaling for TAT andTAG configuration may be employed. The UE may process the RRC messagedifferently compared with the existing mechanisms. When the TAT IE valueindicates infinity (as in existing mechanism), the UE may consider thatthe TAT IE value indicates that the TAT is disabled. The UE may not needto receive a specific message or command to start the TAT of the TAG. Noadditional field is added to the RRC message for this mechanism. Thismechanism may not increase RRC signaling overhead, may reduce MACsignaling overhead and provide an enhanced mechanism with reduced uplinktransmission delay. Equally, one may assume that when the TAT IE valueindicates infinity (as in existing mechanism), the UE may start the TATof the sTAG when the sTAG is configured and the TAT does not expire aslong as the TAG is configured.

In the current uplink time alignment mechanism, the IETimeAlignmentTimer may be used to control how long the UE considers theserving cells belonging to the associated TAG to be uplink time aligned.The value of the IE TimeAlignmentTimer may be in number of sub-frames.For example, a value of sf500 corresponds to 500 sub-frames; sf750corresponds to 750 sub-frames and so on. TimeAlignmentTimer::=ENUMERATED{sf500, sf750, sf1280, sf1920, sf2560, sf5120, sf10240, infinity}.

In existing mechanisms, the eNB may need to initiate a RA process ortransmit a MAC CE for the sTAG no matter what the value of the IETimeAlignmentTimer is. In an example embodiment, when the value of IETimeAlignmentTimer is set to infinity/disabled, there is no need forstarting a RA process or transmitting a MAC CE after a TAG is configuredto enable uplink transmission. For example in such a case, the timealignment timer for sTAG may not be configured, and the sTAG may beconsidered time aligned after the configuration.

In an example embodiment, when the timeAlignmentTimer associated withthe pTAG is not running, the MAC entity may not perform any uplinktransmission on any Serving Cell except the Random Access Preambletransmission on the SpCell.

In an example embodiment, when the IE TimeAlignmentTimer is configuredwith one of the other values {sf500, sf750, sf1280, sf1920, sf2560,sf5120, sf10240}, legacy procedures may be implemented. The UE may nottransmit any uplink signals when TAT is expired or when TAT is notrunning. For example, when TAG is configured and the corresponding TATis not running, the eNB may need to initiate a RA process or transmit aMAC CE to start the TAT of the TAG. When the TAT associated with an sTAGexpires, then for Serving Cells belonging to this TAG: UE may flush HARQbuffers, the UE may notify RRC to release SRS, and/or the UE may notifyRRC to release PUCCH. To start TAT of the TAG, the eNB may transmit oneor more RRC messages to reconfigure SRS and/or PUCCH resources. The UEmay transmit MAC TA CE or initiate a RA process to restart the TAT.

The MAC entity may not perform any uplink transmission on a Serving Cellexcept the Random Access Preamble transmission when the TAT associatedwith the TAG to which this Serving Cell belongs is not running (and TATis not disabled). A MAC entity may store or maintain NTA upon expiry ofassociated TAT. The MAC entity may apply a received TAC MAC CE and maystart associated TAT when the TAT is not running or when the TAT isrunning

In an example embodiment, an RRC message may comprise an IE indicatingthat TAT of an sTAG is disabled. The IE indicating that TAT of an sTAGis disabled or enabled may be different from the IE TimeAlignmentTimer.For example the RRC message may comprise a TAG index IE and aTAT_disabled (or any other name) IE indicating that the TAT of a TAGidentified by the TAG index IE is disabled. For example, the IESTAG-ToAddMod-r11::=SEQUENCE {stag-Id-r11 STAG-Id-r11,timeAlignmentTimerSTAG-r11 TimeAlignmentTimer, . . . } may furtherinclude a timeAlignmentTimerSTAG IE indicating whetherTimeAlignmentTimer of the sTAG is disabled. In that case, the timealignment timer for sTAG may not be configured, and the sTAG may beconsidered time aligned after the configuration. The example embodimentmay provide more flexibility in configuring TAT of a TAG, but requiresan additional field in the RRC message.

When TAT timer of an sTAG is disabled, the eNB may not need to transmita timing advance command to start a TAT of the sTAG. A UE may start SRS,PUCCH, and/or data transmission on the SCell of the TAG as soon as theSCell is activated. A UE may apply the TA value of zero for the initialtransmission. If the network considers the TA value of zero is notaccurate enough, the eNB may adjust the TA via a TA command after thefirst uplink transmission. The UE stores the last updated value of theTA and may use it for the next transmission. For example, when an SCellis deactivated and then activated after a while, the UE may use thestored value of the TA for uplink transmission when the SCell isactivated. When a UE receives a MAC TA CE, the UE may apply a TA in thereceived MAC CE to the stored TA value.

In an example embodiment, a wireless device may receive at least onemessage comprising: configuration parameters of a plurality of cellscomprising a primary cell and at least one secondary cell; a timingadvance group (TAG) index information element (IE) identifying a TAG;and/or a time alignment timer (TAT) IE associated with the TAG. A valueof the TAT IE may be selected from a finite set of predetermined valuescomprising: a first value in terms of subframes; and a second value. Ifthe TAT IE indicates the first value, the wireless device may transmituplink signals on a secondary cell in the TAG only after receiving atiming advance command. If the TAT IE indicates the second value, thewireless device may transmit uplink signals on a the secondary cell inthe TAG without the need for receiving a timing advance command.

In an example embodiment, a wireless device may receive at least onemessage comprising: a timing advance group (TAG) index informationelement (IE) identifying a TAG; and/or a time alignment timer (TAT) IEassociated with the TAG. A value of the TAT IE may be selected from afinite set of predetermined values comprising: a first value; and asecond value. If the TAT IE indicates the first value, the wirelessdevice may transmit uplink signals on a secondary cell in the TAG onlyafter receiving a timing advance command. If the TAT IE indicates thesecond value, the wireless device may transmit uplink signals on a thesecondary cell in the TAG without the need for receiving a timingadvance command

In an example embodiment, the wireless device may receive at least onemessage comprising: configuration parameters of a plurality of cellscomprising a primary cell and at least one secondary cell; a timingadvance group (TAG) index information element (IE) identifying a TAG;and/or one or more time alignment timer (TAT) IEs associated with theTAG. The one or more TAT IEs indicating at least one of: a value of theTAT IE; a TAT of the TAG is disabled. If the TAT IE indicates the value,then the wireless device may transmit uplink signals on a secondary cellin the TAG only after receiving a timing advance command. If the TAT IEindicates that the TAG is disabled, then the wireless device maytransmit uplink signals on the secondary cell in the TAG without theneed for receiving a timing advance command

In an example embodiment, the wireless device may receive at least onemessage comprising: a timing advance group (TAG) index informationelement (IE) identifying a TAG; and/or one or more time alignment timer(TAT) IEs associated with the TAG. The one or more TAT IEs may indicateat least one of: a value of the TAT IE; a TAT of the TAG is disabled. Ifthe TAT IE indicates the value, the wireless device may transmit uplinksignals on a secondary cell in the TAG only after receiving a timingadvance command. If the TAT IE indicates that the TAG is disabled, thewireless device may transmit uplink signals on the secondary cell in theTAG without the need for receiving a timing advance command

In an example embodiment, there may be a need to improve TAT processwhen TAT is configured with one of the values in the legacy system.TimeAlignmentTimer::=ENUMERATED {sf500, sf750, sf1280, sf1920, sf2560,sf5120, sf10240, infinity}.

The TAT of a TAG may start or restart when a UE receives a TAC. In anexample embodiment, a UE may transmit uplink signals when TAT is notrunning employing a TA value. In an example, the TAT may not be runningupon TAG configuration. In an example, the TAT may not be running uponTAT expiration. For example, a UE may transmit uplink signals (e.g. SRS,PUCCH, and/or data) with a TA value of zero when TAT is not running. Inan example embodiment, a UE may transmit uplink signals (e.g. SRS,PUCCH, and/or data) with a previously stored TA value when TAT is notrunning. The stored value of the TA value for an initial uplinktransmission after TAG configuration may be zero. A UE may store themost recently updated value of the TA of a TAG when the TAT of the TAGis expired. A UE may start or restart TAT when the UE receives a TACincluding a TA value from the eNB (as a part of RA process or TAC MACCE). In an example implementation, an eNB may transmit one or more RRCmessages comprising an IE for a TAG to indicate this configuration. TheRRC configuration for a TAG may comprise one or more IE indicating thatUE may transmit uplink signals to an eNB when a corresponding TAT of theTAG is not running Example embodiments may reduce unnecessary MACoverhead and reduce uplink transmission delays when a TAT of an sTAG isnot running

The TAT of a TAG may start or restart when a UE receives a TAC. In anexample embodiment, other trigger conditions may be defined to start orrestart a TAT of a configured TAG. For example, the eNB may configure aUE to start the associated TAT at TAG creation (when TAG is configuredusing RRC messages). In an example embodiment, the eNB may determine ifthe TAG has a suitable TA value. The eNB may transmit at least one RRCmessage to the UE indicating that the UE may start the TAT of a TAG whena TAG is configured. In an example embodiment, other trigger conditionsmay be defined to start or restart a TAT of a configured TAG. In anexample embodiment, a UE may start or restart TAT of a TAG when the UEreceives an uplink grant for an SCell in the TAG. In an exampleembodiment, a UE may start or restart a TAT of a TAG when the UEreceives a MAC A/D command indicating activation of a cell in the TAG.The MAC A/D command may be the first MAC A/D command afterconfiguration. In an example embodiment, a UE may start or restart TATof a TAG when the UE receives a MAC A/D command indicating activation ofa cell in the TAG and uplink signals (e.g. SRS, PUCCH signals, and/orPUSCH) is scheduled/configured for uplink transmission on the TAG. TheMAC A/D command may be the first MAC A/D command after configuration. Inan example implementation, an eNB may transmit one or more RRC messagescomprising an IE for a TAG to indicate such configuration for the UE.Example embodiments may reduce unnecessary MAC overhead and reduceuplink transmission delays when a TAT of an sTAG is not running.

In an example embodiment, a wireless device may receive at least onemessage comprising: a timing advance group (TAG) index informationelement (IE) identifying a TAG; and one or more time alignment timer(TAT) IEs associated with the TAG. The one or more TAT IEs may indicatea value of the TAT IE. The wireless device may transmit uplink signalsemploying a stored value of a timing advance when a TAT of the TAG isnot running

In an example embodiment, a wireless device may receive at least onemessage comprising: a timing advance group (TAG) index informationelement (IE) identifying a TAG; and one or more time alignment timer(TAT) IEs associated with the TAG. The one or more TAT IEs may indicatea value of the TAT IE. The wireless device may start or restart a TAT ofthe TAG when at least one of the following conditions is true: thewireless devices configures the TAG; the wireless devices receives a MACA/D command indicating activation of the cell in the TAG; the wirelessdevices receives a MAC A/D command indicating activation of the cell inthe TAG and uplink signals are scheduled or configured for uplinktransmission on the cell; and/or the wireless device receives an uplinkgrant for the cell in the TAG.

FIG. 24 is an example flow diagram as per an aspect of an embodiment ofthe present invention. At 2410, a wireless device may receive, by awireless device, at least one message comprising a time alignment timer(TAT) information element (IE) associated with a timing advance group(TAG). A value of the TAT IE may be selected from a finite set ofpredetermined values comprising, for example: a first value; and asecond value. According to an embodiment, the first value may relate tosubframes. According to an embodiment, message(s) may further comprisesa TAG index IE identifying the TAG.

The wireless device may transmit uplink signals on a secondary cell inthe TAG (2450) only after receiving a timing advance command (TAC)(determined at 2430) if the TAT IE indicates the first value (determinedat 2420). The wireless device may transmit uplink signals on a secondarycell (2450) regardless of receiving the TAC if the TAT IE indicates thesecond value (determined at 2440). According to an embodiment, the TACmay comprise a TAG index and/or a timing advance value. According to anembodiment, a RAR may comprise a TAC (TAC without the TAG index).According to an embodiment, a random access response may comprise theTAC (TAC without the TAG index). According to an embodiment, thesecondary cell may be a licensed assisted access (LAA) cell.

According to an embodiment, the wireless device may further consider theTAT of the TAG disabled if the TAT IE indicates the second value.According to an embodiment, the wireless device may transmit uplinksignals employing a stored value of a timing advance when a TAT of theTAG is disabled.

FIG. 25 is an example flow diagram as per an aspect of an embodiment ofthe present invention. At 2510, a wireless device may receive, by awireless device, at least one message comprising at least oneinformation element (IE) associated with a timing advance group (TAG).The at least one IE may indicate at least one of: a value of the timealignment timer (TAT) IE, or a TAT of the TAG is disabled. According toan embodiment, the at least one message further comprises a TAG index IEidentifying the TAG. According to an embodiment, the value of the TAT IErelates to subframes.

The wireless device may transmit uplink signals on a secondary cell(2550) in the TAG only after receiving a timing advance command (TAC)(determined at 2530) if the IE indicates the value of the TAT IE(determined at 2520). The wireless device may transmit uplink signals ona secondary cell (2550) regardless of receiving the TAC if the IEindicates that the TAT is disabled (determined at 2540).

According to an embodiment, the wireless device may further receive arandom access response comprising the TAC. According to an embodiment,the wireless device may further transmit uplink signals employing astored value of a timing advance when the TAT of the TAG is disabled.According to an embodiment, the TAC comprises a TAG index and a timingadvance value. According to an embodiment, the secondary cell is alicensed assisted access (LAA) cell.

FIG. 26 is an example flow diagram as per an aspect of an embodiment ofthe present invention. At 2610, a wireless device may receive, by awireless device, at least one message comprising at least one timealignment timer (TAT) information element (IE) associated with a timingadvance group (TAG). The at least one TAT IE may indicate a value of theTAT IE.

The wireless device may start and/or restart the TAT of the TAG inresponse to at least one of, for example, the following: (1) receivingone of the at least one message (2620), (2) receiving a media accesscontrol (MAC) activation/deactivation (A/D) command indicatingactivation of a cell in the TAG (2640), (3) receiving the MAC A/Dcommand indicating activation of the cell in the TAG, and when uplinksignals are scheduled or configured for uplink transmission on the cell(2630), and/or (4) receiving an uplink grant for the cell in the TAG(2650).

According to an embodiment, the at least one message may furthercomprise a TAG index IE identifying the TAG. According to an embodiment,the TAC may comprise a TAG index and a timing advance value. Accordingto an embodiment, the TAG may comprise one or more licensed assistedaccess (LAA) cells. According to an embodiment, the value of the TAT IEmay relate to subframes.

In this specification, “a” and “an” and similar phrases are to beinterpreted as “at least one” and “one or more.” In this specification,the term “may” is to be interpreted as “may, for example.” In otherwords, the term “may” is indicative that the phrase following the term“may” is an example of one of a multitude of suitable possibilities thatmay, or may not, be employed to one or more of the various embodiments.If A and B are sets and every element of A is also an element of B, A iscalled a subset of B. In this specification, only non-empty sets andsubsets are considered. For example, possible subsets of B={cell1,cell2} are: {cell1}, {cell2}, and {cell1, cell2}.

In this specification, parameters (Information elements: IEs) maycomprise one or more objects, and each of those objects may comprise oneor more other objects. For example, if parameter (IE) N comprisesparameter (IE) M, and parameter (IE) M comprises parameter (IE) K, andparameter (IE) K comprises parameter (information element) J, then, forexample, N comprises K, and N comprises J. In an example embodiment,when one or more messages comprise a plurality of parameters, it impliesthat a parameter in the plurality of parameters is in at least one ofthe one or more messages, but does not have to be in each of the one ormore messages.

Many of the elements described in the disclosed embodiments may beimplemented as modules. A module is defined here as an isolatableelement that performs a defined function and has a defined interface toother elements. The modules described in this disclosure may beimplemented in hardware, software in combination with hardware,firmware, wetware (i.e hardware with a biological element) or acombination thereof, all of which are behaviorally equivalent. Forexample, modules may be implemented as a software routine written in acomputer language configured to be executed by a hardware machine (suchas C, C++, Fortran, Java, Basic, Matlab or the like) or amodeling/simulation program such as Simulink, Stateflow, GNU Octave, orLabVIEWMathScript. Additionally, it may be possible to implement modulesusing physical hardware that incorporates discrete or programmableanalog, digital and/or quantum hardware. Examples of programmablehardware comprise: computers, microcontrollers, microprocessors,application-specific integrated circuits (ASICs); field programmablegate arrays (FPGAs); and complex programmable logic devices (CPLDs).Computers, microcontrollers and microprocessors are programmed usinglanguages such as assembly, C, C++ or the like. FPGAs, ASICs and CPLDsare often programmed using hardware description languages (HDL) such asVHSIC hardware description language (VHDL) or Verilog that configureconnections between internal hardware modules with lesser functionalityon a programmable device. Finally, it needs to be emphasized that theabove mentioned technologies are often used in combination to achievethe result of a functional module.

The disclosure of this patent document incorporates material which issubject to copyright protection. The copyright owner has no objection tothe facsimile reproduction by anyone of the patent document or thepatent disclosure, as it appears in the Patent and Trademark Officepatent file or records, for the limited purposes required by law, butotherwise reserves all copyright rights whatsoever.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example, and notlimitation. It will be apparent to persons skilled in the relevantart(s) that various changes in form and detail can be made thereinwithout departing from the spirit and scope. In fact, after reading theabove description, it will be apparent to one skilled in the relevantart(s) how to implement alternative embodiments. Thus, the presentembodiments should not be limited by any of the above describedexemplary embodiments. In particular, it should be noted that, forexample purposes, the above explanation has focused on the example(s)using FDD communication systems. However, one skilled in the art willrecognize that embodiments of the invention may also be implemented in asystem comprising one or more TDD cells (e.g. frame structure 2 and/orframe structure 3—licensed assisted access). The disclosed methods andsystems may be implemented in wireless or wireline systems. The featuresof various embodiments presented in this invention may be combined. Oneor many features (method or system) of one embodiment may be implementedin other embodiments. Only a limited number of example combinations areshown to indicate to one skilled in the art the possibility of featuresthat may be combined in various embodiments to create enhancedtransmission and reception systems and methods.

In addition, it should be understood that any figures which highlightthe functionality and advantages, are presented for example purposesonly. The disclosed architecture is sufficiently flexible andconfigurable, such that it may be utilized in ways other than thatshown. For example, the actions listed in any flowchart may bere-ordered or only optionally used in some embodiments.

Further, the purpose of the Abstract of the Disclosure is to enable theU.S. Patent and Trademark Office and the public generally, andespecially the scientists, engineers and practitioners in the art whoare not familiar with patent or legal terms or phraseology, to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The Abstract of the Disclosureis not intended to be limiting as to the scope in any way.

Finally, it is the applicant's intent that only claims that include theexpress language “means for” or “step for” be interpreted under 35U.S.C. 112, paragraph 6. Claims that do not expressly include the phrase“means for” or “step for” are not to be interpreted under 35 U.S.C. 112.

What is claimed is:
 1. A method comprising: receiving, by a wirelessdevice: at least one radio resource control (RRC) message indicating amaximum counter value; and a control order to transmit a preamble as apart of a random access (RA) procedure on a cell; instructing, aphysical layer by a medium access control (MAC) layer, to transmit thepreamble on the cell; and when a corresponding RA response is notreceived: considering the RA procedure unsuccessfully completed if apreamble transmission counter reaches the maximum counter valueregardless of whether the cell is a licensed or licensed-assisted-access(LAA) cell, wherein the preamble transmission counter is configured tocount a number of physical layer transmissions of the preamble,otherwise considering the RA procedure unsuccessfully completed if apreamble transmission opportunity counter reaches the maximum countervalue and the cell is a LAA cell, wherein: the preamble transmissionopportunity counter is employed only if the cell is a LAA cell, thepreamble transmission opportunity counter is configured to be increasedwhen the physical layer performs listen-before-talk (LBT) fortransmission of the preamble; and the preamble transmission opportunitycounter is configured to limit a time duration that the preamble is usedfor the RA procedure on the cell.
 2. The method of claim 1, furthercomprising setting a preamble power parameter employing the preambletransmission counter.
 3. The method of claim 1, further comprising, inresponse to receiving the control order: starting the preambletransmission counter; and starting the preamble transmission opportunitycounter.
 4. The method of claim 1, further comprising, when the cell isa LAA cell: performing, by the physical layer, LBT for transmission ofthe preamble at a transmission opportunity; transmitting, by thephysical layer, the preamble if the LBT succeeds, otherwise droppingtransmission of the preamble; and receiving, by the MAC layer, a powerramping suspension indication from the physical layer when thetransmission of the preamble is dropped due to a failure of the LBT. 5.A method of claim 1, further comprising considering the RA proceduresuccessfully completed when the wireless device receives thecorresponding RA response.
 6. The method of claim 5, further comprisingselecting RA resources for preamble transmission if: the correspondingRA response is not received; the preamble transmission counter is lessthan the maximum counter value; and the preamble transmissionopportunity counter is less than the maximum counter value.
 7. Themethod of claim 1, wherein the preamble transmission opportunity counteris configured to count a number of transmission opportunities of thepreamble.
 8. The method of claim 1, further comprising monitoring adownlink channel for the corresponding RA response within a RA responsewindow, the corresponding RA response comprising a preamble identifierthat matches the preamble.
 9. The method of claim 1, wherein the controlorder is a physical downlink control channel (PDCCH) comprising apreamble index and a RA mask index.
 10. The method of claim 1, whereinthe at least one RRC message further comprises: configuration parametersof a plurality of cells comprising the cell; RA resource informationelements of a RA channel (RACH) on the cell; a RA response windowinformation element; and a maximum RA transmission counter informationelement.
 11. A method comprising: receiving, by a wireless device, atleast one radio resource control (RRC) message indicating a maximumcounter value; instructing, a physical layer by a medium access control(MAC) layer, to transmit a preamble as a part of a random access (RA)procedure on a licensed assisted access (LAA) cell; performing alisten-before-talk (LBT) for transmission of the preamble at atransmission opportunity of the preamble; when a corresponding RAresponse is not received: increasing a preamble transmission counterwhen the LBT is successful; increasing a preamble transmissionopportunity counter when the LBT is performed regardless of success orfailure of the LBT; and considering the RA procedure unsuccessfullycompleted if the preamble transmission counter reaches the maximumcounter value, otherwise considering the RA procedure unsuccessfullycompleted if the preamble transmission opportunity counter reaches themaximum counter value.
 12. The method of claim 11, further comprisingtransmitting, by the physical layer, the preamble if the LBT succeeds,otherwise dropping transmission of the preamble.
 13. The method of claim11, further comprising considering the RA procedure successfullycompleted when the wireless device receives the corresponding RAresponse.
 14. The method of claim 11, further comprising: receiving acontrol order configured to initiate the RA procedure on the LAA cell;starting the preamble transmission counter in response to receiving thecontrol order; and starting the preamble transmission opportunitycounter in response to receiving the control order.
 15. The method ofclaim 11, further comprising setting a preamble power parameteremploying the preamble transmission counter.
 16. A wireless devicecomprising: one or more processors; and memory storing instructionsthat, when executed by the one or more processors, cause the wirelessdevice to: receive at least one radio resource control (RRC) messageindicating a maximum counter value; instruct, a physical layer by amedium access control (MAC) layer, to transmit a preamble as a part of arandom access (RA) procedure on a licensed assisted access (LAA) cell;perform a listen-before-talk (LBT) for transmission of the preamble at atransmission opportunity of the preamble; when a corresponding RAresponse is not received: increase a preamble transmission counter whenthe LBT is successful; increase a preamble transmission opportunitycounter when the LBT is performed regardless of success or failure ofthe LBT; and consider the RA procedure unsuccessfully completed if thepreamble transmission counter reaches the maximum counter value,otherwise consider the RA procedure unsuccessfully completed if thepreamble transmission opportunity counter reaches the maximum countervalue.
 17. The wireless device of claim 16, wherein the instructions,when executed, further cause the wireless device to transmit, by thephysical layer, the preamble if the LBT succeeds, otherwise droppingtransmission of the preamble.
 18. The wireless device of claim 16,wherein the instructions, when executed, further cause the wirelessdevice to consider the RA procedure successfully completed when thewireless device receives the corresponding RA response.
 19. The wirelessdevice of claim 16, wherein the instructions, when executed, furthercause the wireless device to: receive a control order configured toinitiate the RA procedure on the LAA cell; start the preambletransmission counter in response to receiving the control order; andstart the preamble transmission opportunity counter in response toreceiving the control order.
 20. The wireless device of claim 16,wherein the instructions, when executed, further cause the wirelessdevice to set a preamble power parameter employing the preambletransmission counter.